Amaraba

  • AfSIS
  • Dystric Fluvisols: 50%
  • Gleyic Solonetz: 20%
  • Eutric Regosols: 20%
  • Sodic Planosols: 10%
  • Techniques

Soil properties (estimated): Bama, Naijeria

  • Echenchera okoigwa ekero ekero ogokuna egento
  • pH
  • Bulk density
  • Organic carbon
  • CEC

Challenges
  • Sand dries out rapidly and may lack nutrients because nutrients can be easily washed through the soil with rainfall or irrigation
  • low in organic matter content and native fertility
  • low in ability to retain moisture and nutrients
  • low in cation exchange and buffer capacities
  • rapidly permeable (i.e., rapid movement of water and air)
  • Drains poorly, has few air spaces, warms slowly in spring, heavy to cultivate
[2] [3]
Ebiorokererio
  • Add magnesium to the fertilizer mix to improve yields
Omochakano
  • Sandy clay loam contains 20-35% clay, less than 28% silt, and at least 45% sand
  • Sandy clay contains at least 35% clay and at least 45% sand
[3]
Challenges
  • Peat moss with a pH of 3.0 can be recommended as a soil additive, but peat moss is nutrient-poor, expensive, and it's a nonrenewable resource
[4] [5] [6] [7] [8]
Ebiorokererio
  • The ideal pH range for most crops is 6.5 to 7.0, therefore some crops may require slight pH adjustment for optimal growth
  • To lower soil pH, add a source of acid, such as shredded leaves, sulfur, sawdust or peat moss
  • Add alkaline material such as limestone to decrease soil acidity
  • Apply 2.3 kg of lime per 30 square meters to raise the pH by one point
  • Applying wood ashes will raise soil pH--Wood ashes contain up to 70 percent calcium carbonate, as well as potassium, phosphorus, and many trace elements. Because it is powdery, wood ash is a fast-acting liming material
  • Limit the application of wood ashes to 1 kg per 30 square meters and only apply it every other year in the same area
  • Breed aluminum-tolerant crops
[4] [5] [6] [7]
Omochakano
  • Many plant species are adapted to acidic or alkaline soils
  • The availability of many plant nutrients (for example, P), non-essential elements (for example, Al, Cd, Pb), and essential trace elements (for example, Mn, Fe, Cu, Zn) is strongly dependent on soil pH (Miller and Gardiner 2001)
  • Generally, metal cations (for example, Mn, Fe, Ni, Cu, Zn, Cd, Pb) become more available as pH decreases, while oxyanions (for example, SO4) become more available at alkaline pH levels
  • Soil pH is strongly dependent on the chemical weathering environment. Soils in hot, humid areas and even mesic, wetter areas tend to be more acidic than those of much drier areas. Vegetation communities in those areas tend to be adapted to the soil conditions in which they developed
[9] [10] [11]
Challenges
  • Reduce moderate soil porosity and soil compaction for optimal plant growth
  • As density increases, pore space decreases and the amount of air and water held in the soil also decreases
  • Compaction causes shallow plant rooting, poor plant growth, reduced crop yield, and reduced vegetative cover, and therefore, increased erosion
  • Soil compaction to restrict water movement through the soil profile is beneficial under arid conditions, but under humid conditions compaction decreases yields
  • low soil porosity
  • soil compaction
  • Root penetration is severely impacted on clayey soils at bulk densities greater than 1.47 g/cm3
  • If the compacted layer is very strong, all annual crop roots will fail to penetrate the layer and will end up growing across the face of the layer
[12] [13] [14] [15] [16]
Ebiorokererio
  • Decrease soil disturbance
  • increase soil organic matter
  • Use cover crops, crop residues, perennial sod, and reduced tillage to increase soil organic matter, decrease disturbance, and reduced bulk density
  • Use multi-crop systems involving plants with different rooting depths to help break up compacted soil layers
  • Do not plow or disk to the same depth
  • Do not allow equipment traffic on wet soil
  • Do not burn or remove crop residue
  • Rotate crops with varying root structure and root depth
  • Do not overgraze forage plants
  • Use primer crops to improve the porosity of soils with inherent high bulk density at depth
[12] [13] [14] [15] [16]
Omochakano
  • Soil bulk density may indicate soil compaction but is dependent on many soil factors including particle size distribution, soil organic matter content, and coarse fragment content
  • Bulk density increases as the sand and rock content increases
  • Bulk density decreases as the organic matter content increases
  • A mineral soil with “ideal” physical properties has 50 percent solids and 50 percent pore space occupying a given volume of space
  • At optimal water content, half the pore space is filled with water (such a soil will have a bulk density of 1.33 g/cm3)
  • Roots usually grow well in soils with bulk densities of up to 1.4 g/cm3
  • Root penetration begins to decline significantly at bulk densities above 1.7 g/cm3
  • Above 1.5 g/cm3, there is an increasing probability of adverse effects from soil compaction or high rock content
  • Coarse fragments—Soils with a coarse fragment content of > 50 percent to have a greater probability of adverse effects from infiltration rates that are too high, water storage capacity that is too low, more difficult root penetration, and greater difficulty in seed germination and seedling growth
  • A high contents of coarse fragments can limit soil productivity
[13] [14] [15] [16]
Challenges
  • Difficult to raise organic matter content of well-aerated soils (coarse sands, soils in warm-hot and arid regions) because the added materials decompose rapidly
  • Soil organic matter levels can be maintained with less organic residue in fine-textured soils in cold temperate and moist-wet regions with restricted aeration
[17] [18] [9] [14] [15] [16]
Ebiorokererio
  • Increase the organic matter content by returning organic materials to soils and adding rotations with high-residue crops and deep- or dense-rooting crops
  • Ways to increase organic matter contents of soils: compost, cover crops/green manure crops, crop rotation, perennial forage crops, zero or reduced tillage, agroforestry
[17] [18] [9] [14] [15] [16]
Omochakano
  • Organic Carbon is, together with pH, the best simple indicator of the health status of the soil
  • Soils with very high amounts of organic carbon are generally nutrient-rich, fertile soils with a good structure
  • Very high soil organic carbon (SOC) can be an indicator of good crop yields
  • Total organic carbon in mineral soils (percent): 1 to 5 = adequate levels,
  • > 5 = excellent buildup of organic C with all associated benefits
[17] [18] [9] [14] [15] [16]
Challenges
  • Low CEC soils are more likely to develop potassium and magnesium (and other cation) deficiencies, while high CEC soils are less susceptible to leaching losses of these cations
  • For sandy soils, the addition of a large amount of potassium at one time can lead to high losses due to leaching. This is because the potassium adds a large amount of cations at one time and soil cannot hold on to the excess potassium. Therefore, frequent additions of smaller amounts of potassium can work better to add potassium to the soil than one large amount
Ebiorokererio
  • The lower the CEC, the faster the soil pH will decrease with time
  • Sandy soils require more frequent liming than clay soils
  • The higher the CEC, the larger the quantity of lime that must be added to increase the soil pH
  • Sandy soils need less lime than clay soils to increase the pH to desired levels
  • The higher the CEC, the larger the quantities of soil additives the soil will need to change soil pH, either when increasing pH with lime or high bicarbonate irrigation water, or when decreasing pH with nitrogen fertilizers or elemental sulfur.. Acceptable saturation ranges for Soil CEC = 6-10: 3-5% K, 50-70% Ca, 8-20% Mg
Omochakano
  • A Cation Exchange Capacity (CEC) of 4 to 10 cmol/kg in the soil organic matter (SOM) indicates a low CEC
  • low organic matter
  • low capability to hold important nutrients, such as calcium, magnesium, potassium and sodium
OkonyarekanaDepthEnchera amache amachabu agosokiwaTexture Reaction - pHOrganic Carbon Conductivity - ElectricalSubsoil Cation ExchangeClay Cation ExchangeCalcium Carbonate - LimeGypsum Sodium - Exchangeable
Topsoil27.30.9166210
Subsoil27.30.414583.90
Soil Triangle - Dystric Fluvisols
Goteba engencho yaye - Dystric Fluvisols
  • Fluvisols are very young soils with weak horizon differentiation; they have mostly AC-profiles and are predominantly brown (aerated soils) and/or grey (waterlogged soils) in colour. Their texture can vary from coarse sand in levee soils to heavy clays in basin areas. Most Fluvisols show mottling indicative of alternating reducing and oxidizing conditions. Fluvisols are found on alluvial plains, river fans, valleys and tidal marshes on all continents and in all climate zones. Under natural conditions periodical flooding is fairly common. The soils have a clear evidence of stratification. Soil horizons are weakly developed, but a distinct topsoil horizon may be present. Dystric indicates having a base saturation (by 1 M NH4OAc) of less than 50 percent in the major part between 20 and 100 cm from the soil surface or between 20 cm and continuous rock or a cemented or indurated layer. Major concentrations of Fluvisols are found along rivers and lakes, e.g. in the Amazon Basin, the Ganges Plain of India, the plains near Lake Chad in Central Africa, and the marshlands of Brazil, Paraguay and northern Argentina. Also in deltaic areas, e.g. the deltas of the Ganges–Brahmaputra, Indus, Mekong, Mississippi, Nile, Niger, Orinoco, Po, Rhine, Rio de la Plata, and Zambezi. Furthermore in areas of recent marine deposits, e.g. the coastal lowlands of Sumatra, Kalimantan, Irian Jaya and Papua New Guinea. Paddy rice cultivation is widespread on tropical Fluvisols with satisfactory irrigation and drainage. Paddy land should be dry for at least a few weeks every year in order to prevent the redox potential of the soil from becoming so low that nutritional problems (Fe or H2 S) arise. A dry period also stimulates microbial activity and promotes mineralization of organic matter. Many dryland crops are grown on Fluvisols as well, normally with some form of water control. Tidal lands that are strongly saline are best kept under mangroves or some other salt-tolerant vegetation. Such areas are ecologically valuable and can, with caution, be used for fishing, hunting, salt pans or woodcutting for charcoal or fuelwood. Fluvisols with a thionic horizon or sulphidic material suffer from severe acidity and high levels of Al toxicity
Description - Loam
  • Loams are the most useful "all around" soils; they combine the lightness and earliness of the sands, with the strength and retentiveness of the clays. Loams contain from 40 to 60 per cent, of sand, and 15 to 25 per cent, of clay. They "work up" easily, do not crust or crack, are well supplied with plant food, and, what is chiefly important, water moves through them freely and still they are not leachy. Practically all farm crops grow satisfactorily on a loam. It is especially suitable for potatoes, corn, market-gardening crops, and small fruits; but grasses, cereals, clover, alfalfa, and cotton, find it congenial. It requires no special treatment, except such attention to good tillage, drainage, and the addition of humus as is a necessary part of the best farm practice everywhere. It doesn't matter if peppers are grown in temperate, tropical or subtropical climates as long as they have a relatively dry season, so a good loam that drains well helps to offset a wetter climate. Most fruit trees live longer and produce better when they grow in balanced loam. Citrus trees like good drainage, but they need to be kept moist. Loam is a good choice for citrus
[19]
Ebimeri bia mogondo - Dystric Fluvisols
  • Paddy rice (tropical Fluvisols with irrigation and drainage)
  • dryland crops (water control)
  • mangroves and other salt-tolerant vegetation (strongly saline tidal lands)
[20] [21]
Metrics/Discussion
TopicEkerengoOboime bwa aman'gana
Enchera amache amachabu agosokiwa2
Ebiorokererio
  • Artificial drainage is generally necessary for crop production
Omochakano
  • The presence of only common orange and grey mottles (10–25 percent) indicates the soil is imperfectly drained with only periodic waterlogging
  • wet at a shallow depth for significant periods during the growing season
  • Internal free-water is commonly shallow to moderately deep and transitory to permanent
  • Unless the soil is artificially drained, the growth of most mesophytic plants is restricted
  • low or very low saturated hydraulic conductivity class, or a high water table, or receives water from lateral flow, or persistent rainfall, or some combination of these factors
Goteba engencho yaye
  • Drainage Class soils refers to the frequency and duration of periods when the soil is saturated with water. Alterations of the water regime by human activities, either through drainage or irrigation, are not a consideration unless they have significantly changed the morphology of the soil.

    Seven classes of natural soil drainage are recognized
    • 1. very poorly drained
    • 2. poorly drained
    • 3. somewhat poorly drained
    • 4. moderately well drained
    • 5. well drained
    • 6. somewhat excessively drained
    • 7. excessively drained
[22] [23]
Soil reference depth100 mm
Challenges
  • Soil depth limitations may affect root penetration and may constrain yield formation in roots and tubers
[9] [24]
Goteba engencho yaye
  • An approximation of actual soil depth can be derived through accounting for relevant depth limiting soil phases, obstacles to roots and occurrence of impermeable layers. Soil depth limitations which affect root penetration and may constrain yield formation (roots and tubers).

    This is a measurement in cm of reference soil depth. Reference soil depth of all soil units are set at 100 cm, except for Rendzinas and Rankers of FAO-74 and Leptosols of FAO-90, where the reference soil depth is set at 30 cm, and for Lithosols of FAO-74 and Lithic Leptosols of FAO-90, where it is set at 10 cm
[9] [25]
Base saturation91Igoro ye mia
Challenges
  • low infiltration capacity
  • irrigation is not possible
  • agriculture is limited to crops tolerant to surface waterlogging (e.g. rice, grasses)
  • productivity is low
  • Strongly alkaline soils are often highly sodic (Na reaching toxic levels), badly structured (columnar structure) and easily dispersed surface clays
  • Above a pH of 7.5 (very alkaline), some nutrients such as iron, manganese, and phosphorus are less available
Ebiorokererio
  • To lower soil pH, add a source of acid, such as shredded leaves, sulfur, sawdust or peat moss
Omochakano
  • The base saturation value often shows a near linear correlation with pH
  • Base saturation > 80% indicates saturated soil conditions often calcareous, sometimes sodic or saline
[9]
Goteba engencho yaye
  • The base saturation of the topsoil measures the sum of exchangeable cations (nutrients) Na, Ca, Mg and K as a percentage of the overall exchange capacity of the soil (including the same cations plus H and Al). The value often shows a near linear correlation with pH.

    Critical values as follows
    • Base Saturation < 20 % = desaturated soils, similar interpretation as extremely acid pH
    • Base Saturation of 20 – 50 % = acid conditions
    • Base Saturation of 50 – 80 % = Soil conditions of neutral to slightly alkaline which are ideal conditions for most crops
    • Base Saturation > 80% indicates saturated conditions often calcareous, sometimes sodic or saline
[9] [24]
Calcium carbonate CaCO3 - Lime1% weight
Omochakano
  • Low levels of calcium carbonate enhance soil structure and are generally beneficial for crop production
[9] [26]
Goteba engencho yaye
  • This gives the calcium carbonate (lime) content in the topsoil. Calcium carbonate is a chemical compound (a salt), with the chemical formula CaCO3. It is a common substance found as rock in all parts of the world, and is the main component of shells of marine organisms, snails, and eggshells. Calcium carbonate is the active ingredient in agricultural lime, and is usually the principal cause of hard water. It is quite common in soils particularly in drier areas and it may occur in different forms as mycelium-like threads, as soft powdery lime, as harder concretions or cemented in petrocalcic horizons.

    Low levels of calcium carbonate enhance soil structure and are generally beneficial for crop production but at higher concentrations they may induce iron deficiency and when cemented limit the water storage capacity of soils. In agronomic sense relevant limits are
    • None to very low < 2
    • Low = 2 – 5
    • Moderate = 5 – 15
    • High = 15 – 40
    • Very High > 40
[9]
Organic carbon0.9% weight
Challenges
  • Total organic carbon in mineral soils (percent): 1 to 5 = adequate levels,
  • < 1 = could indicate possible loss of organic C from erosion or other processes, particularly in temperate or colder areas
[17] [18] [9] [14] [15] [16]
Ebiorokererio
  • Increase the organic matter content by returning organic materials to soils and adding rotations with high-residue crops and deep- or dense-rooting crops
  • Ways to increase organic matter contents of soils: compost, cover crops/green manure crops, crop rotation, perennial forage crops, zero or reduced tillage, agroforestry
[17] [18] [9] [14] [15] [16]
Omochakano
  • Organic Carbon is, together with pH, the best simple indicator of the health status of the soil
  • Moderate to high soil organic carbon (SOC) in the soil is an indicator of high crop yields
  • Moderate to high amounts of organic carbon are associated with fertile soils with a good structure
[17] [18] [9] [14] [15] [16]
Goteba engencho yaye
  • This gives the percentage of organic carbon in the topsoil. Organic Carbon is, together with pH, the best simple indicator of the health status of the soil. Moderate to high amounts of organic carbon are associated with fertile soils with a good structure. Soils that are very poor in organic carbon (<0.2%), invariable need organic or inorganic fertilizer application to be productive.

    Soils with an organic matter content of less than 0.6% are considered poor in organic matter. The following classes are suggested to prepare maps of organic carbon status for mineral soils
    • Code 1 < 0.2% organic carbon
    • Code 2 = 0.2 – 0.6% organic carbon
    • Code 3 = 0.6 – 1.2% organic carbon
    • Code 4 = 1.2 – 2.0% organic carbon
    • Code 5 > 2.0% organic carbon
[9] [25]
Cation exchange capacity - clay62 cmol/kg
Challenges
  • Having a larger CEC values is an indicator that the soil has a greater capacity to hold cations
  • A high CEC soil has a greater capacity to hold cations, so higher rates of fertilizer or lime are often required to change a high CEC soil
  • high CEC is an indicator that there is a high reserve of nutrients in the soil
  • Soils with low CEC can take a large amount of fertilizer or lime to correct
  • A high CEC soil requires a higher soil cation level, or soil test, to provide adequate crop nutrition
Ebiorokererio
  • The higher the CEC, the larger the quantities of soil additives the soil will need to change soil pH, either when increasing pH with lime or high bicarbonate irrigation water, or when decreasing pH with nitrogen fertilizers or elemental sulfur
Omochakano
  • CEC in the range of 50 to 100 cmol/kg clay indicates a high CEC with soils containing mixed clay with illite present
  • CEC is highly dependent upon soil texture and organic matter content
  • Generally, the higher the contents of clay and organic matter in the soil, the higher the CEC
  • CEC of most soils increases with an increase in soil pH
  • Very acid soils will have high concentrations of H+ and Al3+
  • In neutral to moderately alkaline soils, Ca2+ and Mg2+ dominate
  • Poorly drained arid soils may adsorb Na in very high quantities
  • Only a small percentage of the essential plant nutrient cations (K +, Ca 2+, Mg 2+, and NH4+) will be ‘loose’ in the soil water and thus available for plant uptake, therefore the CEC is important because it provides a reservoir of nutrients
  • Cations in the soil water that are leached below the rootzone by water are replaced by cations formerly bound to the CEC
  • ‘Buffer capacity’ exists for cation nutrients as well as soil pH
  • The cation exchange capacity (CEC) of illite is smaller than that of smectite but higher than that of kaolinite
Goteba engencho yaye
  • This gives the cation exchange capacity of the clay fraction in topsoil. The type of clay mineral dominantly present in the soil is often characterizes a specific set of pedogenetic factors in which the soil has developed. Tropical, leaching climates produce the clay mineral kaolinite, while confined conditions rich in Ca and Mg in climates with a pronounced dry season encourage the formation of the clay mineral smectite (montmorillonite).

    Nutrient retention capacity is of particular importance for the effectiveness of fertilizer applications and is therefore of special relevance for intermediate and high input level cropping conditions. Nutrient retention capacity refers to the capacity of the soil to retain added nutrients against losses caused by leaching. Plant nutrients are held in the soil on the exchange sites provided by the clay fraction, organic matter and the clay-humus complex. Losses vary with the intensity of leaching which is determined by the rate of drainage of soil moisture through the soil profile. Clay minerals have typical exchange capacities, with kaolinites generally having the lowest at less than 16 cmol/kg, while smectites have one of the highest with a CEC per 100g clay being 80 cmol/kg, or more. The classes generally used in the Harmonized World Soil Database are
    • Class 1 = < 20 cmol/kg clay (kaolinite dominant)
    • Class 2 = 20-50 cmol/kg clay (mixed with kaolinite present)
    • Class 3 = >50-100 cmol/kg clay (mixed, illite)
    • Class 4 = >100 cmol/kg clay (montmorillonite)
    NOTE: Soils developed on volcanic materials rich in amorphous sesquioxides may have very higher values (over 150 cmol/kg)
[9]
Cation exchange capacity - amaraba16 cmol/kg
Challenges
  • Having a larger CEC values is an indicator that the soil has a greater capacity to hold cations
  • A high CEC soil has a greater capacity to hold cations, so higher rates of fertilizer or lime are often required to change a high CEC soil
  • high CEC is an indicator that there is a high reserve of nutrients in the soil
  • Soils with low CEC can take a large amount of fertilizer or lime to correct
  • A high CEC soil requires a higher soil cation level, or soil test, to provide adequate crop nutrition
Ebiorokererio
  • The higher the CEC, the larger the quantity of lime that must be added to increase the soil pH
  • Sandy soils need less lime than clay soils to increase the pH to desired levels
  • The higher the CEC, the larger the quantities of soil additives the soil will need to change soil pH, either when increasing pH with lime or high bicarbonate irrigation water, or when decreasing pH with nitrogen fertilizers or elemental sulfur.. Acceptable saturation ranges for Soil CEC = 6-10: 3-5% K, 50-70% Ca, 8-20% Mg
Goteba engencho yaye
  • This gives the cation exchange capacity in the topsoil. The total nutrient fixing capacity of a soil is well expressed by its Cation Exchange Capacity. Soils with low CEC have little resilience and can not build up stores of nutrients. Many sandy soils have CEC less than 4 cmol/kg. The clay content, the clay type and the organic matter content all determine the total nutrient storage capacity.

    Nutrient retention capacity is of particular importance for the effectiveness of fertilizer applications and is therefore of special relevance for intermediate and high input level cropping conditions. Nutrient retention capacity refers to the capacity of the soil to retain added nutrients against losses caused by leaching. Plant nutrients are held in the soil on the exchange sites provided by the clay fraction, organic matter and the clay-humus complex. Losses vary with the intensity of leaching which is determined by the rate of drainage of soil moisture through the soil profile. Values in excess of 10 cmol/kg are considered satisfactory for most crops. This is reflected by the following code system used in the Harmonized World Soil Database
    • Code 1 = Cation Exchange Capacity < 4 cmol/kg
    • Code 2 = Cation Exchange Capacity of 4-10 cmol/kg
    • Code 3 = Cation Exchange Capacity > 10 -- 20 cmol/kg
    • Code 4 = Cation Exchange Capacity > 20 -- 40 cmol/kg
    • Code 5 = Cation Exchange Capacity > 40 cmol/kg
[9] [25]
Clay - Percent - weight20% weight
Challenges
  • Drains poorly, has few air spaces, warms slowly in spring, heavy to cultivate
  • Adverse physical properties
  • Poor workability
  • Require too much management for success in low-technology societies
  • Tree crops cannot root in the subsoil
  • Tree roots are damaged as the soil shrinks and swells
  • Low structural stability
  • Very susceptible to water erosion
Ebiorokererio
  • Do not use slopes above 5 percent for arable cropping
  • Use groundcover crops on slopes less than 5 percent
  • When terracing, use surface drainage to prevent slumping
  • Add organic matter to improve the tilth, workability, and internal drainage
  • If drainage is improved, plants can grow well in clayey soils since clay holds more nutrients than many other soils
  • Use caution when plowing and tilling
  • Do not plow excessively wet clays, or they will become cloddy
  • Till clay soils only when they are dry and crumble readily
  • In temperate climates, Plow clay soils in the fall, then leave them rough and exposed to the mellowing action of freezing and thawing
  • Frequent, shallow tillage can help to prevent crusting of the topsoil
  • Maize crops require deep cultivation and ridges in the soil to improve drainage (maize cannot tolerate waterlogging and can die if it stands in water for as long as 2 days)
  • Adding lime to clay soils can improve the soil's texture to result in looser and more porous soil
  • Use under-drainage to reduce the soil's heaviness by removing the extra water during dry periods
  • Under-drainage promotes aeration and warmth in clay soils
  • Loosen clay soils by mixing them with humus or sand
  • Barnyard manure or a green manure crop will lighten heavy clay soil
  • To lighten clay soil, spread sand on top of the clay soil and plow it under
[27] [28] [29] [2]
Omochakano
  • The feel of clay soils is slick or lumpy and sticky when very wet, and hard and smooth when dry
[3] [30]
Goteba engencho yaye
  • This measure the percentage of clay in the topsoil. Clay is naturally occurring firm earthy material, composed primarily of fine-grained (diameter less than 0.002mm) that is plastic when wet and hardens when heated and that consists primarily of hydrated silicates or aluminum. Clay is mostly composed of clay minerals which are phyllo-silicate minerals and minerals which impart plasticity and harden when fired or dried. The definition of "fine grained" used above is particles smaller than 2 µm, colloid chemists (and Eastern European soil scientists) may use 1 µm.

    The clay content of the soil is listed as a percentage (0 to 100) of the total weight of the soil. Soils is with a high percentage of clay, such as Vertisols, are used for very extensive (grazing, collection of fuelwood, and charcoal burning) through smallholder post-rainy season crop production (millet, sorghum, cotton and chickpeas) to small-scale (rice) and large-scale irrigated agriculture (cotton, wheat, barley, sorghum, chickpeas, flax, noug [Guzotia abessynica] and sugar cane). Cotton is known to perform well on Vertisols, allegedly because cotton has a vertical root system that is not damaged severely by cracking of the soil. Tree crops are generally less successful because tree roots find it difficult to establish themselves in the subsoil and are damaged as the soil shrinks and swells. Management practices for crop production should be directed primarily at water control in combination with conservation or improvement of soil fertility
[9]
Gravel - Percent - volume4% weight
Challenges
  • Gravel can affect the rooting conditions and workability of soils
  • May be low in organic matter
[9] [31] [32] [33]
Ebiorokererio
  • Add organic matter
  • fertilize regularly
  • Use pea gravel as a mulch to protect the roots of herbs and other drought-tolerant plants
  • Pea gravel reflects heat and provides good drainage
[9] [31] [32] [33]
Goteba engencho yaye
  • This measures the volume percentage of gravel in the topsoil. Gravel stands for the percentage of materials in a soil that are larger than 2 mm.

    Gravel can affect the rooting conditions and workability of soils. The percentage of gravel in the soil is listed on a scale of 0 to 100 percent volume
[29] [34]
Sand - Percent - weight39% weight
Challenges
  • Sand dries out rapidly and may lack nutrients because nutrients can be easily washed through the soil with rainfall or irrigation
  • low in organic matter content and native fertility
  • low in ability to retain moisture and nutrients
  • low in cation exchange and buffer capacities
  • rapidly permeable (i.e., rapid movement of water and air)
  • In the perhumid tropics, sandy soils are chemically exhausted and highly sensitive to erosion
Ebiorokererio
  • Use frequent irrigation, artificial drainage, and proper fertilization (more frequent but lower quantities of nutrients per application)
  • Total amounts of fertilizer per crop are usually quite high
  • Manage erosion and chemical exhaustion in perhumid tropical soils
  • Add organic matter to improve texture, increase water-holding capacity, and improve fertility
[35] [2] [3] [36] [37] [38]
Omochakano
  • Sand is free-draining, has a gritty feel, warms quickly, and is easy to cultivate
  • Feel is gritty, not sticky
[3]
Goteba engencho yaye
  • Sand comprises particles, or granules, ranging in diameter from 0.0625 mm (or 1/16 mm) to 2 millimeters. An individual particle in this range size is termed a sand grain. Sand feels gritty when rubbed between the fingers (silt, by comparison, feels like flour).

    This measures the percentage (0 to 100) by weight of sand in the topsoil. Sand is commonly divided into five sub-categories based on size
    • very fine sand (1/16 - 1/8 mm diameter)
    • fine sand (1/8 mm - 1/4 mm)
    • medium sand (1/4 mm - 1/2 mm)
    • coarse sand (1/2 mm - 1 mm)
    • and very coarse sand (1 mm - 2 mm)
[9] [25]
Silt - Percent - weight41% weight
Challenges
  • erosion
[39]
Ebiorokererio
  • Tillage and erosion control measures such as terracing, contour plowing, mulching and use of cover crops help to conserve the soil from compaction and serious structure deterioration
  • Fertilizers and/or lime are preconditions for continuous cultivation
[40] [41] [39]
Omochakano
  • Silty soils have a weak structure (break up easily)
  • easy to work
  • The feel of silt is smooth and soapy
  • Feel is smooth or flour-like when rubbed between the thumb and fingers
  • makes a weak ribbon (less than 2.5 cm long)
[40]
Goteba engencho yaye
  • Silt is produced by the mechanical weathering of rock, as opposed to the chemical weathering that results in clays. This mechanical weathering can be due to grinding by glaciers, eolian abrasion (sandblasting by the wind) as well as water erosion of rocks on the beds of rivers and streams. Silt is sometimes known as 'rock flour' or 'stone dust', especially when produced by glacial action. Mineralogically, silt is composed mainly of quartz and feldspar.

    This measures the percentage (0 to 100) by weight of silt in the topsoil. Soils with a lot of silt make excellent farm land, but erode easily. Erosion removes topsoil, reduces levels of soil organic matter, and contributes to the breakdown of soil structure. This creates a less favorable environment for plant growth. Soil erosion can be avoided by: maintaining a protective cover on the soil, creating a barrier to the erosive agent, modifying the landscape to control runoff amounts and rates. Specific practices to avoid water erosion: growing forage crops in rotation or as permanent cover; growing winter cover crops; interseeding; protecting the surface with crop residue; shortening the length and steepness of slopes; increasing water infiltration rates; improving aggregate stability. Specific practices to avoid wind erosion: maintaining a cover of plants or residue, planting shelterbelts, stripcropping, increase surface roughness, cultivating on the contour, maintaining soil aggregates at a size less likely to be carried by wind
[9]
Electrical conductivity0.1 dS/m
Challenges
  • inhibited uptake of water
  • irrigation and waterlogging can cause excess soil salinity
[25] [42]
Ebiorokererio
  • Control soil salinity by permitting 10-20% of the irrigation water to leach the soil, and then be drained and discharged
[25] [42]
Omochakano
  • ECe, or electrical conductivity, is a measure of soil salinity
[9]
Goteba engencho yaye
  • This gives the electrical conductivity of the topsoil. Coastal and desert soils in particular can be enriched with water-soluble salts or salts more soluble than gypsum. The salt content of a soil can be roughly estimated from the Electrical Conductivity of the soil (EC, expressed in dS/m) measured in a saturated soil paste or a more diluted suspension of soil in water.

    Accumulation of salts may cause salinity. Excess of free salts referred to as soil salinity is measured as Electric Conductivity (EC in dS/m) or as saturation of the exchange complex with sodium ions. Salinity affects crops through inhibiting the uptake of water. Moderate salinity affects growth and reduces yields; high salinity levels may kill the crop. Crops vary considerably in their resistance and response to salt in soils. Some crops will suffer at values as little as 2 dS/m (spinach) others can stand up to 16 dS/m (date palm). Agronomic relevant limits are
    • Very low ECe < 2 dS/m
    • Low ECe = 2 – 4 dS/m
    • Moderate ECe = 4 – 8 dS/m
    • High ECe = 8 – 16 dS/m
    • Very High ECe > 16 dS/m
    Some plants are more tolerant to a high salt concentration than others. Highly tolerant plants include date palm, barley, sugarbeet, cotton, asparagus, spinach
[9] [25]
Gypsum content CaSO40% volume
Ebiorokererio
  • Using water culture to increase the concentration of SO4 mixture (K2SO4 + MgSO4) increases the uptake of NO3, K, Mg and sulphur but decreases the uptake of Ca and P
  • Use soil terracing to prevent erosion
  • Use supplementary irrigation to increase productivity where water resources are available
  • Harrow the land after harvesting and before the rainy season to improve the infiltration of water and conserve soil moisture
  • Increase organic matter by replacing fallow by small-grain leguminous crops in the wheat-fallow rotations
  • Add manure
  • Use subsoiling to break the cemented gypsic subsoil to improve root penetration and reduces susceptibility to drought, especially in the case of fruit and forest trees
  • Do not mix the topsoil and subsoil
  • Apply nitrogen and phosphorus to cereals
  • N is generally applied where rainfall exceeds 260 mm annually
  • Phosphorus fertilizers increase the yield of cereals, especially under low rainfall
  • For irrigated gypsiferous soils: The use of (NH4)2CO3 solution was found to cause the optimum elimination of gypsum in gypsiferous soils with both low and high levels of gypsum; In general, there is need for ample nitrogen fertilizers for crops grown on gypsiferous soils, especially under irrigated agriculture. There are no significant differences between the requirements of crops for nitrogen on gypsiferous and non-gypsiferous soils; Molybdenum applications might benefit many plants, especially legumes
[43] [9]
Omochakano
  • Up to 2 percent gypsum in the soil favors plant growth
  • Most agricultural crops thrive in soils with no to very low gypsum content
Goteba engencho yaye
  • Calcium sulphate (gypsum) content in topsoil. Gypsum is a chemical compound (a salt) which occurs occasionally in soils particularly in the driest areas of the globe where it can occur in a flower-like form typically opaque with embedded sand grains called desert rose. In soils it may occur in fibers, crystals or soft. Research indicates that up to 2 percent gypsum in the soil favours plant growth, between 2 and 25 percent has little or no adverse effect if in powdery form, but more than 25 percent can cause substantial reduction in yields. It is suggested that reductions are due in part to imbalanced ion ratios, particularly K:Ca and Mg:Ca.

    Gypsum strongly limits available soil moisture. Tolerance of crops to gypsum varies widely (FAO, 1990; Sys, 1993). Relevant limits are considered the following
    • None to very low CaSO4 < 2%
    • Low CaSO4 = 2 – 5%
    • Moderate CaSO4 = 5 – 25%
    • High CaSO4 = 25 – 40%
    • Very High CaSO4 > 40%
Soil reaction - pH7.3 -log H+
Challenges
  • Above a pH of 7.5 (very alkaline), some nutrients such as iron, manganese, and phosphorus are less available
  • Peat moss with a pH of 3.0 can be recommended as a soil additive, but peat moss is nutrient-poor, expensive, and it's a nonrenewable resource
[4] [5] [6] [7] [8]
Ebiorokererio
  • To lower soil pH, add a source of acid, such as shredded leaves, sulfur, sawdust or peat moss
[4] [5] [6] [7]
Omochakano
  • Many plant species are adapted to acidic or alkaline soils
  • The availability of many plant nutrients (for example, P), non-essential elements (for example, Al, Cd, Pb), and essential trace elements (for example, Mn, Fe, Cu, Zn) is strongly dependent on soil pH (Miller and Gardiner 2001)
  • Generally, metal cations (for example, Mn, Fe, Ni, Cu, Zn, Cd, Pb) become more available as pH decreases, while oxyanions (for example, SO4) become more available at alkaline pH levels
  • Soil pH is strongly dependent on the chemical weathering environment. Soils in hot, humid areas and even mesic, wetter areas tend to be more acidic than those of much drier areas. Vegetation communities in those areas tend to be adapted to the soil conditions in which they developed
[9] [10] [11]
Goteba engencho yaye
  • This gives the soil reaction of subsoil. pH, measured in a soil-water solution, is a measure for the acidity and alkalinity of the soil.

    Five major pH classes are considered here that have specific agronomic significance
    • pH < 4.5 = Extremely acid soils include Acid Sulfate Soils (Mangrove soils, cat clays). Do not drain because by oxidation sulfuric acid will be produced and pH will drop lower still
    • pH 4.5 – 5.5 = Very acid soils suffering often from Al toxicity. Some crops are tolerant for these conditions (Tea, Pineapple)
    • pH 5.5 –7.2 = Acid to neutral soils - these are the best pH conditions for nutrient availability and suitable for most crops
    • pH 7.2 – 8.5 = These pH values are indicative of carbonate rich soils. Depending on the form and concentration of calcium carbonate they may result in well structured soils which may however have depth limitations when the calcium carbonate hardens in an impermeable layer and chemically forms less available carbonates affecting nutrient availability (Phosphorus, Iron)
    • pH > 8.5 = Indicates alkaline soils often highly sodic (Na reaching toxic levels), badly structured (columnar structure) and easily dispersed surface clays
[9] [44]
Exchangeable sodium2Igoro ye mia
Challenges
  • Sodicity causes sodium toxicity and affects soil structure leading to massive or coarse columnar structure with low permeability to water and roots
  • low infiltration rate
  • poorly aerated
  • difficult to cultivate
  • sodic soils can adversely affect plant growth
  • high pH lowers availability of some essential plant nutrients, such as calcium, magnesium, P, Fe, Mn, and Zn
  • risk of toxic levels of sodium, molybdenum, and boron
Goteba engencho yaye
  • This gives the exchangeable sodium percentage in the topsoil. The exchangeable sodium percentage has been used to indicate levels of sodium in soils it is calculated as the ratio of Na in the CEC (or sum of cations) ESP= Na*100/CECsoil. Alternatively SAR (Sodium Adsorption Ratio) has been used (SAR= Na/Square root ((Ca+Mg)/2)) to indicate levels of sodium hazards for crops.

    Excess of free salts referred to as saturation of the exchange complex with sodium ions, which is referred to as sodicity or sodium alkalinity and is measured as Exchangeable Sodium Percentage (ESP). Sodicity causes sodium toxicity and affects soil structure leading to massive or coarse columnar structure with low permeability. Sodic soils have a low infiltration rate, they are poorly aerated and difficult to cultivate. Thus, sodic soils adversely affect the plants' growth. Agronomic relevant limits are
    • Low ESP < 6%
    • Moderate ESP = 6 – 15%
    • High ESP = 15 – 25%
    • Very High ESP > 25%
[9] [25]
Reference bulk density1.36 kg/dm3
Ebiorokererio
  • To reduce high bulk density and compaction, minimize soil disturbance and production activities when soils are wet, use designated field roads or rows for equipment traffic, reduce the number of trips across the area, and maintain or increase soil organic matter
  • Use grazing systems that minimize livestock traffic and loafing, provide protected heavy use areas, and adhere to recommended minimum grazing heights
  • Use conservation crop rotation, cover crop, deep tillage, prescribed grazing residue, and tillage management
  • Avoid plowing, timber harvesting, or compaction of the soil
[13] [14] [15] [16]
Omochakano
  • Soil bulk density may indicate soil compaction but is dependent on many soil factors including particle size distribution, soil organic matter content, and coarse fragment content
  • Bulk density increases as the sand and rock content increases
  • Bulk density decreases as the organic matter content increases
  • A mineral soil with “ideal” physical properties has 50 percent solids and 50 percent pore space occupying a given volume of space
  • At optimal water content, half the pore space is filled with water (such a soil will have a bulk density of 1.33 g/cm3)
  • Roots usually grow well in soils with bulk densities of up to 1.4 g/cm3
  • Root penetration begins to decline significantly at bulk densities above 1.7 g/cm3
  • Above 1.5 g/cm3, there is an increasing probability of adverse effects from soil compaction or high rock content
  • Coarse fragments—Soils with a coarse fragment content of > 50 percent to have a greater probability of adverse effects from infiltration rates that are too high, water storage capacity that is too low, more difficult root penetration, and greater difficulty in seed germination and seedling growth
  • A high contents of coarse fragments can limit soil productivity
[13] [14] [15] [16]
Goteba engencho yaye
  • Reference bulk density is a property of particulate materials. It is the mass of many particles of the material divided by the volume they occupy. The volume includes the space between particles as well as the space inside the pores of individual particles.

    This is a measurement in kg/dm3 of the topsoil reference bulk density. Bulk density reflects the soil’s ability to function for structural support, water and solute movement, and soil aeration. High bulk density is an indicator of low soil porosity and soil compaction. It may cause restrictions to root growth, and poor movement of air and water through the soil. Compaction can result in shallow plant rooting and poor plant growth, influencing crop yield and reducing vegetative cover available to protect soil from erosion. By reducing water infiltration into the soil, compaction can lead to increased runoff and erosion from sloping land or waterlogged soils in flatter areas. In general, some soil compaction to restrict water movement through the soil profile is beneficial under arid conditions, but under humid conditions compaction decreases yields. On cropland, long-term solutions to bulk density and soil compaction problems revolve around decreasing soil disturbance and increasing soil organic matter. A system that uses cover crops, crop residues, perennial sod, and/or reduced tillage results in increased soil organic matter, less disturbance and reduced bulk density. Additionally, the use of multi-crop systems involving plants with different rooting depths can help break up compacted soil layers
[9] [41] [45]
Nitrogen (N)
Challenges
  • Too much nitrogen in soil can harm plants
  • Adding nitrogen is easy, but removing excess nitrogen in soil is more difficult
  • Too much nitrogen in soil reduces the ability of plants to fruit and flower
[46] [14] [15] [47]
Ebiorokererio
  • Organic methods of adding nitrogen to the soil include: adding composted manure to the soil, planting a green manure crop such as borage, planting nitrogen-fixing plants such as peas or beans, and adding coffee grounds to the soil, but be careful when adding coffee grounds as this practice also creates acidity and lowers pH of the soil. Organic methods require more time than inorganic methods, but they can result in a more even distribution of the added nitrogen. Non-organic methods of adding nitrogen to the soil include the use of chemical fertilizers. A high-nitrogen fertilizer will have a high first number in the NPK ratio, for example 10-10-10. Nitrogen-containing chemical fertilizers act quickly to add nitrogen to the soil, but the nitrogen also leaves the soil quickly. If there is too much nitrogen in the soil, plant squash, cabbage, broccoli or maize which will use up large amounts of nitrogen while they grow. Note: while these plants absorb the excess nitrogen in the soil, they may look unhealthy and may produce low yields
[46] [14] [15] [47]
Omochakano
  • Total nitrogen in mineral soils (percent): > 0.5 = High – excellent reserve of nitrogen
  • 0.1 to 0.5 = Moderate – adequate levels
  • < 0.1 = Low – could indicate loss of organic N
  • Nitrogen is essential for plant growth. Plants will not grow or produce without sufficient nitrogen
  • When legumes and other nitrogen fixing plants and the bacteria called Rhizobium work together to store the nitrogen, they are creating a green warehouse in the soil. While they are growing, they release very little nitrogen into the soil, but when they are done growing and they die, their decomposition release the stored nitrogen and increases the total nitrogen in soil. Their death makes nitrogen for plants available later on. When the plant stores the nitrogen in the roots, it produces a lump on the root called a nitrogen nodule. This is harmless to the plant but very beneficial to the farm
[46] [14] [15] [47]
Phosphorus (P)
Challenges
  • Generally, it is difficult for plants to absorb phosphorus (P) so it is usually not a concern that plants will absorb too much P.: Plants grown in soils with Olsen-extractable P levels above 10 mg/kg usually will not respond to added P
  • Do not overuse P: soils with very high levels of extractable P may have a deleterious effect on water quality if such soils are subjected to erosion and the soil particles end up in receiving waters
[48] [14] [15] [47]
Ebiorokererio
  • For inorganic farms, use phosphate-containing fertilizers, such as N-P-K with a high P value (the middle value)
  • Use bone meal or rock phosphate to correct a phosphorus deficiency
  • Add compost to the soil to help plants take up the phosphorus that is already in the soil
[48] [14] [15] [47]
Omochakano
  • Phosphorus is one of the essential nutrients required for plant growth and development. It helps plants convert other nutrients in order for the plant to grow
  • Phosphorus is the "P" component of N-P-K fertilizers. The availability of soil P to plants depends on the forms of P in soils and soil pH
  • In acid soils, most plant-available P is associated with Fe and Al oxides and is best extracted with the Bray 1 extractant (0.03 M NH4F + 0.025 M HCl). The Bray 1 extractant is applicable to soils with a pH below 6.8, but not to near-neutral or alkaline soils because the acid in the extract begins to dissolve Ca phosphates. These Ca phosphates usually release only small amounts of P for plant uptake unless they begin to dissolve under more acid conditions. Generally, deficiency symptoms are not exhibited by plants growing in soils with Bray 1 levels above 15 mg/kg (Soil and Plant Analysis Council 1999)
  • In alkaline soils, most soil P is associated with Ca, either sorbed to carbonate minerals or existing as various Ca phosphate minerals, the most common of which is apatite. The Olsen (pH 8.5, 0.5 M NaHCO3) extractant was developed to measure plant-available P in alkaline soils, but it also works in many acid soils. The bicarbonate ions release P sorbed to many mineral surfaces that is plant available without dissolving the otherwise plant-unavailable P in Ca phosphates
[48] [14] [15] [47]
Potassium (K)
Ebiorokererio
  • Potassium fertilizer is sometimes called potash fertilizer
  • high potassium fertilizer contains only potassium (K) or has a high K value
  • Compost made primarily from food byproducts, especially banana peels, is an excellent source of potassium for the soil when used as a soil additive
  • Use wood ash as a light application to avoid burning plants
  • Greensand can be used as a soil additive to add potassium to the soil
  • Because potassium deficiency in plants is difficult to diagnose visually, test the soil before adding more potassium
[49] [14] [15] [47]
Omochakano
  • With all plants, potassium assists all functions within the plant. When a plant has enough potassium, it will simply be a better overall plant
  • Potassium is important to plant growth and development. Potassium helps: plants grow faster, use water better and be more drought resistant, fight off disease, resist pests, grow stronger, and produce more crops
  • K (mg/kg): > 500 = High – excellent reserve
  • 100 to 500 = Moderate – adequate levels for most plants
  • < 100 = Low – possible deficiencies
[49] [14] [15] [47]
OkonyarekanaDepthEnchera amache amachabu agosokiwaTexture Reaction - pHOrganic Carbon Conductivity - ElectricalSubsoil Cation ExchangeClay Cation ExchangeCalcium Carbonate - LimeGypsum Sodium - Exchangeable
Topsoil27.20.716575.20
Subsoil27.20.29216490.1
Soil Triangle - Gleyic Solonetz
Goteba engencho yaye - Gleyic Solonetz
  • Gleyic refers to having a layer within 100 cm from the mineral soil surface that is at least 25 cm thick and which has reducing conditions in some parts and a gleyic colour pattern throughout. This pattern is essentially made up of reddish, brownish or yellowish colours at ped surfaces and/or in the upper soil layer or layers, in combination with greyish/bluish colours inside the peds and/or deeper in the soil. Solonetz are soils with a dense, strongly structured, clayey subsurface horizon that has a high proportion of adsorbed Na and/or Mg ions. Solonetz that contain free soda (Na2CO3) are strongly alkaline (field pH > 8.5). Solonetz soils have a black or brown surface soil over over a natric horizon with strong round-topped columnar structure elements within the upper 100 cm of the soil profile. There is a subsurface horizon (subsoil), higher in clay content than the upper horizon, that has more than 15% exchangeable sodium. Solonetz zones are associated with gleysols, solonchaks and kastanozems. In USA soil taxonomy, solonetz corresponds to sodium-rich aridisols and mollisols. Solonetz occur predominantly in areas with a steppe climate (dry summers and an annual precipitation sum of not more than 400 to 500 mm), in particular in flat lands with impeded vertical and lateral drainage. Smaller occurrences are found on inherently saline parent materials (e.g. marine clays or saline alluvial deposits). Worldwide, Solonetz cover some 135 million hectares. Major Solonetz areas are found in the Ukraine, Russia, Kazakhstan, Hungary, Bulgaria, Rumania, China, USA, Canada, South Africa and Australia
Description - Loam
  • Loams are the most useful "all around" soils; they combine the lightness and earliness of the sands, with the strength and retentiveness of the clays. Loams contain from 40 to 60 per cent, of sand, and 15 to 25 per cent, of clay. They "work up" easily, do not crust or crack, are well supplied with plant food, and, what is chiefly important, water moves through them freely and still they are not leachy. Practically all farm crops grow satisfactorily on a loam. It is especially suitable for potatoes, corn, market-gardening crops, and small fruits; but grasses, cereals, clover, alfalfa, and cotton, find it congenial. It requires no special treatment, except such attention to good tillage, drainage, and the addition of humus as is a necessary part of the best farm practice everywhere. It doesn't matter if peppers are grown in temperate, tropical or subtropical climates as long as they have a relatively dry season, so a good loam that drains well helps to offset a wetter climate. Most fruit trees live longer and produce better when they grow in balanced loam. Citrus trees like good drainage, but they need to be kept moist. Loam is a good choice for citrus
[19]
Ebimeri bia mogondo - Gleyic Solonetz
  • arable farming
[50] [51]
Metrics/Discussion
TopicEkerengoOboime bwa aman'gana
Enchera amache amachabu agosokiwa2
Ebiorokererio
  • Artificial drainage is generally necessary for crop production
Omochakano
  • The presence of only common orange and grey mottles (10–25 percent) indicates the soil is imperfectly drained with only periodic waterlogging
  • wet at a shallow depth for significant periods during the growing season
  • Internal free-water is commonly shallow to moderately deep and transitory to permanent
  • Unless the soil is artificially drained, the growth of most mesophytic plants is restricted
  • low or very low saturated hydraulic conductivity class, or a high water table, or receives water from lateral flow, or persistent rainfall, or some combination of these factors
Goteba engencho yaye
  • Drainage Class soils refers to the frequency and duration of periods when the soil is saturated with water. Alterations of the water regime by human activities, either through drainage or irrigation, are not a consideration unless they have significantly changed the morphology of the soil.

    Seven classes of natural soil drainage are recognized
    • 1. very poorly drained
    • 2. poorly drained
    • 3. somewhat poorly drained
    • 4. moderately well drained
    • 5. well drained
    • 6. somewhat excessively drained
    • 7. excessively drained
[22] [23]
Soil reference depth100 mm
Challenges
  • Soil depth limitations may affect root penetration and may constrain yield formation in roots and tubers
[9] [24]
Goteba engencho yaye
  • An approximation of actual soil depth can be derived through accounting for relevant depth limiting soil phases, obstacles to roots and occurrence of impermeable layers. Soil depth limitations which affect root penetration and may constrain yield formation (roots and tubers).

    This is a measurement in cm of reference soil depth. Reference soil depth of all soil units are set at 100 cm, except for Rendzinas and Rankers of FAO-74 and Leptosols of FAO-90, where the reference soil depth is set at 30 cm, and for Lithosols of FAO-74 and Lithic Leptosols of FAO-90, where it is set at 10 cm
[9] [25]
Base saturation93Igoro ye mia
Challenges
  • low infiltration capacity
  • irrigation is not possible
  • agriculture is limited to crops tolerant to surface waterlogging (e.g. rice, grasses)
  • productivity is low
  • Strongly alkaline soils are often highly sodic (Na reaching toxic levels), badly structured (columnar structure) and easily dispersed surface clays
  • Above a pH of 7.5 (very alkaline), some nutrients such as iron, manganese, and phosphorus are less available
Ebiorokererio
  • To lower soil pH, add a source of acid, such as shredded leaves, sulfur, sawdust or peat moss
Omochakano
  • The base saturation value often shows a near linear correlation with pH
  • Base saturation > 80% indicates saturated soil conditions often calcareous, sometimes sodic or saline
[9]
Goteba engencho yaye
  • The base saturation of the topsoil measures the sum of exchangeable cations (nutrients) Na, Ca, Mg and K as a percentage of the overall exchange capacity of the soil (including the same cations plus H and Al). The value often shows a near linear correlation with pH.

    Critical values as follows
    • Base Saturation < 20 % = desaturated soils, similar interpretation as extremely acid pH
    • Base Saturation of 20 – 50 % = acid conditions
    • Base Saturation of 50 – 80 % = Soil conditions of neutral to slightly alkaline which are ideal conditions for most crops
    • Base Saturation > 80% indicates saturated conditions often calcareous, sometimes sodic or saline
[9] [24]
Calcium carbonate CaCO3 - Lime5.2% weight
Challenges
  • Higher concentrations of calcium carbonate may induce iron deficiency and when cemented limit the water storage capacity of soils
  • Cemented conditions of the subsoil layers may hamper root development and water movement characteristics
  • low in organic matter and available nitrogen
  • high pH level results in unavailability of phosphate (formation of unavailable calcium phosphates as apatite) and sometimes reduced micronutrient availability, e.g. zinc and iron (lime induced chlorosis) and cause problems of potassium and magnesium nutrition as a result of the nutritional imbalance between these elements and calcium
Ebiorokererio
  • Iron deficiency can be corrected with foliar applications of ferrous sulfate or fast acting soluble iron chelates
  • Soil applications of soluble forms of iron last longer but the plant response is slower because it has to be picked up by the plant roots and translocated up to the leaves
  • Soluble iron applied to soil with iron deficiency problems are often quickly oxidized to more insoluble forms, thus making them unavailable
Omochakano
  • Calcareous soils are relatively alkaline
  • high pH
  • very weak acidity of carbonic acid
Goteba engencho yaye
  • This gives the calcium carbonate (lime) content in the topsoil. Calcium carbonate is a chemical compound (a salt), with the chemical formula CaCO3. It is a common substance found as rock in all parts of the world, and is the main component of shells of marine organisms, snails, and eggshells. Calcium carbonate is the active ingredient in agricultural lime, and is usually the principal cause of hard water. It is quite common in soils particularly in drier areas and it may occur in different forms as mycelium-like threads, as soft powdery lime, as harder concretions or cemented in petrocalcic horizons.

    Low levels of calcium carbonate enhance soil structure and are generally beneficial for crop production but at higher concentrations they may induce iron deficiency and when cemented limit the water storage capacity of soils. In agronomic sense relevant limits are
    • None to very low < 2
    • Low = 2 – 5
    • Moderate = 5 – 15
    • High = 15 – 40
    • Very High > 40
[9]
Organic carbon0.7% weight
Challenges
  • Total organic carbon in mineral soils (percent): 1 to 5 = adequate levels,
  • < 1 = could indicate possible loss of organic C from erosion or other processes, particularly in temperate or colder areas
[17] [18] [9] [14] [15] [16]
Ebiorokererio
  • Increase the organic matter content by returning organic materials to soils and adding rotations with high-residue crops and deep- or dense-rooting crops
  • Ways to increase organic matter contents of soils: compost, cover crops/green manure crops, crop rotation, perennial forage crops, zero or reduced tillage, agroforestry
[17] [18] [9] [14] [15] [16]
Omochakano
  • Organic Carbon is, together with pH, the best simple indicator of the health status of the soil
  • Moderate to high soil organic carbon (SOC) in the soil is an indicator of high crop yields
  • Moderate to high amounts of organic carbon are associated with fertile soils with a good structure
[17] [18] [9] [14] [15] [16]
Goteba engencho yaye
  • This gives the percentage of organic carbon in the topsoil. Organic Carbon is, together with pH, the best simple indicator of the health status of the soil. Moderate to high amounts of organic carbon are associated with fertile soils with a good structure. Soils that are very poor in organic carbon (<0.2%), invariable need organic or inorganic fertilizer application to be productive.

    Soils with an organic matter content of less than 0.6% are considered poor in organic matter. The following classes are suggested to prepare maps of organic carbon status for mineral soils
    • Code 1 < 0.2% organic carbon
    • Code 2 = 0.2 – 0.6% organic carbon
    • Code 3 = 0.6 – 1.2% organic carbon
    • Code 4 = 1.2 – 2.0% organic carbon
    • Code 5 > 2.0% organic carbon
[9] [25]
Cation exchange capacity - clay57 cmol/kg
Challenges
  • Having a larger CEC values is an indicator that the soil has a greater capacity to hold cations
  • A high CEC soil has a greater capacity to hold cations, so higher rates of fertilizer or lime are often required to change a high CEC soil
  • high CEC is an indicator that there is a high reserve of nutrients in the soil
  • Soils with low CEC can take a large amount of fertilizer or lime to correct
  • A high CEC soil requires a higher soil cation level, or soil test, to provide adequate crop nutrition
Ebiorokererio
  • The higher the CEC, the larger the quantities of soil additives the soil will need to change soil pH, either when increasing pH with lime or high bicarbonate irrigation water, or when decreasing pH with nitrogen fertilizers or elemental sulfur
Omochakano
  • CEC in the range of 50 to 100 cmol/kg clay indicates a high CEC with soils containing mixed clay with illite present
  • CEC is highly dependent upon soil texture and organic matter content
  • Generally, the higher the contents of clay and organic matter in the soil, the higher the CEC
  • CEC of most soils increases with an increase in soil pH
  • Very acid soils will have high concentrations of H+ and Al3+
  • In neutral to moderately alkaline soils, Ca2+ and Mg2+ dominate
  • Poorly drained arid soils may adsorb Na in very high quantities
  • Only a small percentage of the essential plant nutrient cations (K +, Ca 2+, Mg 2+, and NH4+) will be ‘loose’ in the soil water and thus available for plant uptake, therefore the CEC is important because it provides a reservoir of nutrients
  • Cations in the soil water that are leached below the rootzone by water are replaced by cations formerly bound to the CEC
  • ‘Buffer capacity’ exists for cation nutrients as well as soil pH
  • The cation exchange capacity (CEC) of illite is smaller than that of smectite but higher than that of kaolinite
Goteba engencho yaye
  • This gives the cation exchange capacity of the clay fraction in topsoil. The type of clay mineral dominantly present in the soil is often characterizes a specific set of pedogenetic factors in which the soil has developed. Tropical, leaching climates produce the clay mineral kaolinite, while confined conditions rich in Ca and Mg in climates with a pronounced dry season encourage the formation of the clay mineral smectite (montmorillonite).

    Nutrient retention capacity is of particular importance for the effectiveness of fertilizer applications and is therefore of special relevance for intermediate and high input level cropping conditions. Nutrient retention capacity refers to the capacity of the soil to retain added nutrients against losses caused by leaching. Plant nutrients are held in the soil on the exchange sites provided by the clay fraction, organic matter and the clay-humus complex. Losses vary with the intensity of leaching which is determined by the rate of drainage of soil moisture through the soil profile. Clay minerals have typical exchange capacities, with kaolinites generally having the lowest at less than 16 cmol/kg, while smectites have one of the highest with a CEC per 100g clay being 80 cmol/kg, or more. The classes generally used in the Harmonized World Soil Database are
    • Class 1 = < 20 cmol/kg clay (kaolinite dominant)
    • Class 2 = 20-50 cmol/kg clay (mixed with kaolinite present)
    • Class 3 = >50-100 cmol/kg clay (mixed, illite)
    • Class 4 = >100 cmol/kg clay (montmorillonite)
    NOTE: Soils developed on volcanic materials rich in amorphous sesquioxides may have very higher values (over 150 cmol/kg)
[9]
Cation exchange capacity - amaraba16 cmol/kg
Challenges
  • Having a larger CEC values is an indicator that the soil has a greater capacity to hold cations
  • A high CEC soil has a greater capacity to hold cations, so higher rates of fertilizer or lime are often required to change a high CEC soil
  • high CEC is an indicator that there is a high reserve of nutrients in the soil
  • Soils with low CEC can take a large amount of fertilizer or lime to correct
  • A high CEC soil requires a higher soil cation level, or soil test, to provide adequate crop nutrition
Ebiorokererio
  • The higher the CEC, the larger the quantity of lime that must be added to increase the soil pH
  • Sandy soils need less lime than clay soils to increase the pH to desired levels
  • The higher the CEC, the larger the quantities of soil additives the soil will need to change soil pH, either when increasing pH with lime or high bicarbonate irrigation water, or when decreasing pH with nitrogen fertilizers or elemental sulfur.. Acceptable saturation ranges for Soil CEC = 6-10: 3-5% K, 50-70% Ca, 8-20% Mg
Goteba engencho yaye
  • This gives the cation exchange capacity in the topsoil. The total nutrient fixing capacity of a soil is well expressed by its Cation Exchange Capacity. Soils with low CEC have little resilience and can not build up stores of nutrients. Many sandy soils have CEC less than 4 cmol/kg. The clay content, the clay type and the organic matter content all determine the total nutrient storage capacity.

    Nutrient retention capacity is of particular importance for the effectiveness of fertilizer applications and is therefore of special relevance for intermediate and high input level cropping conditions. Nutrient retention capacity refers to the capacity of the soil to retain added nutrients against losses caused by leaching. Plant nutrients are held in the soil on the exchange sites provided by the clay fraction, organic matter and the clay-humus complex. Losses vary with the intensity of leaching which is determined by the rate of drainage of soil moisture through the soil profile. Values in excess of 10 cmol/kg are considered satisfactory for most crops. This is reflected by the following code system used in the Harmonized World Soil Database
    • Code 1 = Cation Exchange Capacity < 4 cmol/kg
    • Code 2 = Cation Exchange Capacity of 4-10 cmol/kg
    • Code 3 = Cation Exchange Capacity > 10 -- 20 cmol/kg
    • Code 4 = Cation Exchange Capacity > 20 -- 40 cmol/kg
    • Code 5 = Cation Exchange Capacity > 40 cmol/kg
[9] [25]
Clay - Percent - weight23% weight
Challenges
  • Drains poorly, has few air spaces, warms slowly in spring, heavy to cultivate
  • Adverse physical properties
  • Poor workability
  • Require too much management for success in low-technology societies
  • Tree crops cannot root in the subsoil
  • Tree roots are damaged as the soil shrinks and swells
  • Low structural stability
  • Very susceptible to water erosion
Ebiorokererio
  • Do not use slopes above 5 percent for arable cropping
  • Use groundcover crops on slopes less than 5 percent
  • When terracing, use surface drainage to prevent slumping
  • Add organic matter to improve the tilth, workability, and internal drainage
  • If drainage is improved, plants can grow well in clayey soils since clay holds more nutrients than many other soils
  • Use caution when plowing and tilling
  • Do not plow excessively wet clays, or they will become cloddy
  • Till clay soils only when they are dry and crumble readily
  • In temperate climates, Plow clay soils in the fall, then leave them rough and exposed to the mellowing action of freezing and thawing
  • Frequent, shallow tillage can help to prevent crusting of the topsoil
  • Maize crops require deep cultivation and ridges in the soil to improve drainage (maize cannot tolerate waterlogging and can die if it stands in water for as long as 2 days)
  • Adding lime to clay soils can improve the soil's texture to result in looser and more porous soil
  • Use under-drainage to reduce the soil's heaviness by removing the extra water during dry periods
  • Under-drainage promotes aeration and warmth in clay soils
  • Loosen clay soils by mixing them with humus or sand
  • Barnyard manure or a green manure crop will lighten heavy clay soil
  • To lighten clay soil, spread sand on top of the clay soil and plow it under
[27] [28] [29] [2]
Omochakano
  • The feel of clay soils is slick or lumpy and sticky when very wet, and hard and smooth when dry
[3] [30]
Goteba engencho yaye
  • This measure the percentage of clay in the topsoil. Clay is naturally occurring firm earthy material, composed primarily of fine-grained (diameter less than 0.002mm) that is plastic when wet and hardens when heated and that consists primarily of hydrated silicates or aluminum. Clay is mostly composed of clay minerals which are phyllo-silicate minerals and minerals which impart plasticity and harden when fired or dried. The definition of "fine grained" used above is particles smaller than 2 µm, colloid chemists (and Eastern European soil scientists) may use 1 µm.

    The clay content of the soil is listed as a percentage (0 to 100) of the total weight of the soil. Soils is with a high percentage of clay, such as Vertisols, are used for very extensive (grazing, collection of fuelwood, and charcoal burning) through smallholder post-rainy season crop production (millet, sorghum, cotton and chickpeas) to small-scale (rice) and large-scale irrigated agriculture (cotton, wheat, barley, sorghum, chickpeas, flax, noug [Guzotia abessynica] and sugar cane). Cotton is known to perform well on Vertisols, allegedly because cotton has a vertical root system that is not damaged severely by cracking of the soil. Tree crops are generally less successful because tree roots find it difficult to establish themselves in the subsoil and are damaged as the soil shrinks and swells. Management practices for crop production should be directed primarily at water control in combination with conservation or improvement of soil fertility
[9]
Gravel - Percent - volume5% weight
Challenges
  • Gravel can affect the rooting conditions and workability of soils
  • May be low in organic matter
[9] [31] [32] [33]
Ebiorokererio
  • Add organic matter
  • fertilize regularly
  • Use pea gravel as a mulch to protect the roots of herbs and other drought-tolerant plants
  • Pea gravel reflects heat and provides good drainage
[9] [31] [32] [33]
Goteba engencho yaye
  • This measures the volume percentage of gravel in the topsoil. Gravel stands for the percentage of materials in a soil that are larger than 2 mm.

    Gravel can affect the rooting conditions and workability of soils. The percentage of gravel in the soil is listed on a scale of 0 to 100 percent volume
[29] [34]
Sand - Percent - weight36% weight
Challenges
  • Sand dries out rapidly and may lack nutrients because nutrients can be easily washed through the soil with rainfall or irrigation
  • low in organic matter content and native fertility
  • low in ability to retain moisture and nutrients
  • low in cation exchange and buffer capacities
  • rapidly permeable (i.e., rapid movement of water and air)
  • In the perhumid tropics, sandy soils are chemically exhausted and highly sensitive to erosion
Ebiorokererio
  • Use frequent irrigation, artificial drainage, and proper fertilization (more frequent but lower quantities of nutrients per application)
  • Total amounts of fertilizer per crop are usually quite high
  • Manage erosion and chemical exhaustion in perhumid tropical soils
  • Add organic matter to improve texture, increase water-holding capacity, and improve fertility
[35] [2] [3] [36] [37] [38]
Omochakano
  • Sand is free-draining, has a gritty feel, warms quickly, and is easy to cultivate
  • Feel is gritty, not sticky
[3]
Goteba engencho yaye
  • Sand comprises particles, or granules, ranging in diameter from 0.0625 mm (or 1/16 mm) to 2 millimeters. An individual particle in this range size is termed a sand grain. Sand feels gritty when rubbed between the fingers (silt, by comparison, feels like flour).

    This measures the percentage (0 to 100) by weight of sand in the topsoil. Sand is commonly divided into five sub-categories based on size
    • very fine sand (1/16 - 1/8 mm diameter)
    • fine sand (1/8 mm - 1/4 mm)
    • medium sand (1/4 mm - 1/2 mm)
    • coarse sand (1/2 mm - 1 mm)
    • and very coarse sand (1 mm - 2 mm)
[9] [25]
Silt - Percent - weight41% weight
Challenges
  • erosion
[39]
Ebiorokererio
  • Tillage and erosion control measures such as terracing, contour plowing, mulching and use of cover crops help to conserve the soil from compaction and serious structure deterioration
  • Fertilizers and/or lime are preconditions for continuous cultivation
[40] [41] [39]
Omochakano
  • Silty soils have a weak structure (break up easily)
  • easy to work
  • The feel of silt is smooth and soapy
  • Feel is smooth or flour-like when rubbed between the thumb and fingers
  • makes a weak ribbon (less than 2.5 cm long)
[40]
Goteba engencho yaye
  • Silt is produced by the mechanical weathering of rock, as opposed to the chemical weathering that results in clays. This mechanical weathering can be due to grinding by glaciers, eolian abrasion (sandblasting by the wind) as well as water erosion of rocks on the beds of rivers and streams. Silt is sometimes known as 'rock flour' or 'stone dust', especially when produced by glacial action. Mineralogically, silt is composed mainly of quartz and feldspar.

    This measures the percentage (0 to 100) by weight of silt in the topsoil. Soils with a lot of silt make excellent farm land, but erode easily. Erosion removes topsoil, reduces levels of soil organic matter, and contributes to the breakdown of soil structure. This creates a less favorable environment for plant growth. Soil erosion can be avoided by: maintaining a protective cover on the soil, creating a barrier to the erosive agent, modifying the landscape to control runoff amounts and rates. Specific practices to avoid water erosion: growing forage crops in rotation or as permanent cover; growing winter cover crops; interseeding; protecting the surface with crop residue; shortening the length and steepness of slopes; increasing water infiltration rates; improving aggregate stability. Specific practices to avoid wind erosion: maintaining a cover of plants or residue, planting shelterbelts, stripcropping, increase surface roughness, cultivating on the contour, maintaining soil aggregates at a size less likely to be carried by wind
[9]
Electrical conductivity0.1 dS/m
Challenges
  • inhibited uptake of water
  • irrigation and waterlogging can cause excess soil salinity
[25] [42]
Ebiorokererio
  • Control soil salinity by permitting 10-20% of the irrigation water to leach the soil, and then be drained and discharged
[25] [42]
Omochakano
  • ECe, or electrical conductivity, is a measure of soil salinity
[9]
Goteba engencho yaye
  • This gives the electrical conductivity of the topsoil. Coastal and desert soils in particular can be enriched with water-soluble salts or salts more soluble than gypsum. The salt content of a soil can be roughly estimated from the Electrical Conductivity of the soil (EC, expressed in dS/m) measured in a saturated soil paste or a more diluted suspension of soil in water.

    Accumulation of salts may cause salinity. Excess of free salts referred to as soil salinity is measured as Electric Conductivity (EC in dS/m) or as saturation of the exchange complex with sodium ions. Salinity affects crops through inhibiting the uptake of water. Moderate salinity affects growth and reduces yields; high salinity levels may kill the crop. Crops vary considerably in their resistance and response to salt in soils. Some crops will suffer at values as little as 2 dS/m (spinach) others can stand up to 16 dS/m (date palm). Agronomic relevant limits are
    • Very low ECe < 2 dS/m
    • Low ECe = 2 – 4 dS/m
    • Moderate ECe = 4 – 8 dS/m
    • High ECe = 8 – 16 dS/m
    • Very High ECe > 16 dS/m
    Some plants are more tolerant to a high salt concentration than others. Highly tolerant plants include date palm, barley, sugarbeet, cotton, asparagus, spinach
[9] [25]
Gypsum content CaSO40% volume
Ebiorokererio
  • Using water culture to increase the concentration of SO4 mixture (K2SO4 + MgSO4) increases the uptake of NO3, K, Mg and sulphur but decreases the uptake of Ca and P
  • Use soil terracing to prevent erosion
  • Use supplementary irrigation to increase productivity where water resources are available
  • Harrow the land after harvesting and before the rainy season to improve the infiltration of water and conserve soil moisture
  • Increase organic matter by replacing fallow by small-grain leguminous crops in the wheat-fallow rotations
  • Add manure
  • Use subsoiling to break the cemented gypsic subsoil to improve root penetration and reduces susceptibility to drought, especially in the case of fruit and forest trees
  • Do not mix the topsoil and subsoil
  • Apply nitrogen and phosphorus to cereals
  • N is generally applied where rainfall exceeds 260 mm annually
  • Phosphorus fertilizers increase the yield of cereals, especially under low rainfall
  • For irrigated gypsiferous soils: The use of (NH4)2CO3 solution was found to cause the optimum elimination of gypsum in gypsiferous soils with both low and high levels of gypsum; In general, there is need for ample nitrogen fertilizers for crops grown on gypsiferous soils, especially under irrigated agriculture. There are no significant differences between the requirements of crops for nitrogen on gypsiferous and non-gypsiferous soils; Molybdenum applications might benefit many plants, especially legumes
[43] [9]
Omochakano
  • Up to 2 percent gypsum in the soil favors plant growth
  • Most agricultural crops thrive in soils with no to very low gypsum content
Goteba engencho yaye
  • Calcium sulphate (gypsum) content in topsoil. Gypsum is a chemical compound (a salt) which occurs occasionally in soils particularly in the driest areas of the globe where it can occur in a flower-like form typically opaque with embedded sand grains called desert rose. In soils it may occur in fibers, crystals or soft. Research indicates that up to 2 percent gypsum in the soil favours plant growth, between 2 and 25 percent has little or no adverse effect if in powdery form, but more than 25 percent can cause substantial reduction in yields. It is suggested that reductions are due in part to imbalanced ion ratios, particularly K:Ca and Mg:Ca.

    Gypsum strongly limits available soil moisture. Tolerance of crops to gypsum varies widely (FAO, 1990; Sys, 1993). Relevant limits are considered the following
    • None to very low CaSO4 < 2%
    • Low CaSO4 = 2 – 5%
    • Moderate CaSO4 = 5 – 25%
    • High CaSO4 = 25 – 40%
    • Very High CaSO4 > 40%
Soil reaction - pH7.2 -log H+
Challenges
  • Above a pH of 7.5 (very alkaline), some nutrients such as iron, manganese, and phosphorus are less available
  • Peat moss with a pH of 3.0 can be recommended as a soil additive, but peat moss is nutrient-poor, expensive, and it's a nonrenewable resource
[4] [5] [6] [7] [8]
Ebiorokererio
  • To lower soil pH, add a source of acid, such as shredded leaves, sulfur, sawdust or peat moss
[4] [5] [6] [7]
Omochakano
  • Many plant species are adapted to acidic or alkaline soils
  • The availability of many plant nutrients (for example, P), non-essential elements (for example, Al, Cd, Pb), and essential trace elements (for example, Mn, Fe, Cu, Zn) is strongly dependent on soil pH (Miller and Gardiner 2001)
  • Generally, metal cations (for example, Mn, Fe, Ni, Cu, Zn, Cd, Pb) become more available as pH decreases, while oxyanions (for example, SO4) become more available at alkaline pH levels
  • Soil pH is strongly dependent on the chemical weathering environment. Soils in hot, humid areas and even mesic, wetter areas tend to be more acidic than those of much drier areas. Vegetation communities in those areas tend to be adapted to the soil conditions in which they developed
[9] [10] [11]
Goteba engencho yaye
  • This gives the soil reaction of subsoil. pH, measured in a soil-water solution, is a measure for the acidity and alkalinity of the soil.

    Five major pH classes are considered here that have specific agronomic significance
    • pH < 4.5 = Extremely acid soils include Acid Sulfate Soils (Mangrove soils, cat clays). Do not drain because by oxidation sulfuric acid will be produced and pH will drop lower still
    • pH 4.5 – 5.5 = Very acid soils suffering often from Al toxicity. Some crops are tolerant for these conditions (Tea, Pineapple)
    • pH 5.5 –7.2 = Acid to neutral soils - these are the best pH conditions for nutrient availability and suitable for most crops
    • pH 7.2 – 8.5 = These pH values are indicative of carbonate rich soils. Depending on the form and concentration of calcium carbonate they may result in well structured soils which may however have depth limitations when the calcium carbonate hardens in an impermeable layer and chemically forms less available carbonates affecting nutrient availability (Phosphorus, Iron)
    • pH > 8.5 = Indicates alkaline soils often highly sodic (Na reaching toxic levels), badly structured (columnar structure) and easily dispersed surface clays
[9] [44]
Exchangeable sodium11Igoro ye mia
Challenges
  • Sodicity causes sodium toxicity and affects soil structure leading to massive or coarse columnar structure with low permeability to water and roots
  • low infiltration rate
  • poorly aerated
  • difficult to cultivate
  • sodic soils can adversely affect plant growth
  • high pH lowers availability of some essential plant nutrients, such as calcium, magnesium, P, Fe, Mn, and Zn
  • risk of toxic levels of sodium, molybdenum, and boron
Ebiorokererio
  • To improve sodic soils, remove most of the exchangeable sodium and replace with calcium ions in the root zone
  • reclaim soil slowly and at low cost by long-continued irrigated cropping
  • planting rice and sodic-tolerant crops, and adding organic residues and/or farmyard manure
  • For quick amendment of soil sodicity, apply gypsum or calcium chloride then leach the soil to remove the salts derived from the reaction of the amendment with the sodic soil
  • Add organic matter (i.e. straw, farm and green manures) to help dissolve the calcium compounds in the soils
Omochakano
  • Soils with an ESP of > 15 percent are classified as sodic or saline/sodic soils depending on the salt content of the soils as measured by the electrical conductivity of a saturated soil extract (Richards 1954)
  • Sodic soils are found in more aridic areas of the United States
  • Sodic soils are more likely to exhibit adverse effects (for example, decreased infiltration) associated with too high Na levels than soils with an ESP < 15 percent
[9]
Goteba engencho yaye
  • This gives the exchangeable sodium percentage in the topsoil. The exchangeable sodium percentage has been used to indicate levels of sodium in soils it is calculated as the ratio of Na in the CEC (or sum of cations) ESP= Na*100/CECsoil. Alternatively SAR (Sodium Adsorption Ratio) has been used (SAR= Na/Square root ((Ca+Mg)/2)) to indicate levels of sodium hazards for crops.

    Excess of free salts referred to as saturation of the exchange complex with sodium ions, which is referred to as sodicity or sodium alkalinity and is measured as Exchangeable Sodium Percentage (ESP). Sodicity causes sodium toxicity and affects soil structure leading to massive or coarse columnar structure with low permeability. Sodic soils have a low infiltration rate, they are poorly aerated and difficult to cultivate. Thus, sodic soils adversely affect the plants' growth. Agronomic relevant limits are
    • Low ESP < 6%
    • Moderate ESP = 6 – 15%
    • High ESP = 15 – 25%
    • Very High ESP > 25%
[9] [25]
Reference bulk density1.32 kg/dm3
Ebiorokererio
  • To reduce high bulk density and compaction, minimize soil disturbance and production activities when soils are wet, use designated field roads or rows for equipment traffic, reduce the number of trips across the area, and maintain or increase soil organic matter
  • Use grazing systems that minimize livestock traffic and loafing, provide protected heavy use areas, and adhere to recommended minimum grazing heights
  • Use conservation crop rotation, cover crop, deep tillage, prescribed grazing residue, and tillage management
  • Avoid plowing, timber harvesting, or compaction of the soil
[13] [14] [15] [16]
Omochakano
  • Soil bulk density may indicate soil compaction but is dependent on many soil factors including particle size distribution, soil organic matter content, and coarse fragment content
  • Bulk density increases as the sand and rock content increases
  • Bulk density decreases as the organic matter content increases
  • A mineral soil with “ideal” physical properties has 50 percent solids and 50 percent pore space occupying a given volume of space
  • At optimal water content, half the pore space is filled with water (such a soil will have a bulk density of 1.33 g/cm3)
  • Roots usually grow well in soils with bulk densities of up to 1.4 g/cm3
  • Root penetration begins to decline significantly at bulk densities above 1.7 g/cm3
  • Above 1.5 g/cm3, there is an increasing probability of adverse effects from soil compaction or high rock content
  • Coarse fragments—Soils with a coarse fragment content of > 50 percent to have a greater probability of adverse effects from infiltration rates that are too high, water storage capacity that is too low, more difficult root penetration, and greater difficulty in seed germination and seedling growth
  • A high contents of coarse fragments can limit soil productivity
[13] [14] [15] [16]
Goteba engencho yaye
  • Reference bulk density is a property of particulate materials. It is the mass of many particles of the material divided by the volume they occupy. The volume includes the space between particles as well as the space inside the pores of individual particles.

    This is a measurement in kg/dm3 of the topsoil reference bulk density. Bulk density reflects the soil’s ability to function for structural support, water and solute movement, and soil aeration. High bulk density is an indicator of low soil porosity and soil compaction. It may cause restrictions to root growth, and poor movement of air and water through the soil. Compaction can result in shallow plant rooting and poor plant growth, influencing crop yield and reducing vegetative cover available to protect soil from erosion. By reducing water infiltration into the soil, compaction can lead to increased runoff and erosion from sloping land or waterlogged soils in flatter areas. In general, some soil compaction to restrict water movement through the soil profile is beneficial under arid conditions, but under humid conditions compaction decreases yields. On cropland, long-term solutions to bulk density and soil compaction problems revolve around decreasing soil disturbance and increasing soil organic matter. A system that uses cover crops, crop residues, perennial sod, and/or reduced tillage results in increased soil organic matter, less disturbance and reduced bulk density. Additionally, the use of multi-crop systems involving plants with different rooting depths can help break up compacted soil layers
[9] [41] [45]
Nitrogen (N)
Challenges
  • Too much nitrogen in soil can harm plants
  • Adding nitrogen is easy, but removing excess nitrogen in soil is more difficult
  • Too much nitrogen in soil reduces the ability of plants to fruit and flower
[46] [14] [15] [47]
Ebiorokererio
  • Organic methods of adding nitrogen to the soil include: adding composted manure to the soil, planting a green manure crop such as borage, planting nitrogen-fixing plants such as peas or beans, and adding coffee grounds to the soil, but be careful when adding coffee grounds as this practice also creates acidity and lowers pH of the soil. Organic methods require more time than inorganic methods, but they can result in a more even distribution of the added nitrogen. Non-organic methods of adding nitrogen to the soil include the use of chemical fertilizers. A high-nitrogen fertilizer will have a high first number in the NPK ratio, for example 10-10-10. Nitrogen-containing chemical fertilizers act quickly to add nitrogen to the soil, but the nitrogen also leaves the soil quickly. If there is too much nitrogen in the soil, plant squash, cabbage, broccoli or maize which will use up large amounts of nitrogen while they grow. Note: while these plants absorb the excess nitrogen in the soil, they may look unhealthy and may produce low yields
[46] [14] [15] [47]
Omochakano
  • Total nitrogen in mineral soils (percent): > 0.5 = High – excellent reserve of nitrogen
  • 0.1 to 0.5 = Moderate – adequate levels
  • < 0.1 = Low – could indicate loss of organic N
  • Nitrogen is essential for plant growth. Plants will not grow or produce without sufficient nitrogen
  • When legumes and other nitrogen fixing plants and the bacteria called Rhizobium work together to store the nitrogen, they are creating a green warehouse in the soil. While they are growing, they release very little nitrogen into the soil, but when they are done growing and they die, their decomposition release the stored nitrogen and increases the total nitrogen in soil. Their death makes nitrogen for plants available later on. When the plant stores the nitrogen in the roots, it produces a lump on the root called a nitrogen nodule. This is harmless to the plant but very beneficial to the farm
[46] [14] [15] [47]
Phosphorus (P)
Challenges
  • Generally, it is difficult for plants to absorb phosphorus (P) so it is usually not a concern that plants will absorb too much P.: Plants grown in soils with Olsen-extractable P levels above 10 mg/kg usually will not respond to added P
  • Do not overuse P: soils with very high levels of extractable P may have a deleterious effect on water quality if such soils are subjected to erosion and the soil particles end up in receiving waters
[48] [14] [15] [47]
Ebiorokererio
  • For inorganic farms, use phosphate-containing fertilizers, such as N-P-K with a high P value (the middle value)
  • Use bone meal or rock phosphate to correct a phosphorus deficiency
  • Add compost to the soil to help plants take up the phosphorus that is already in the soil
[48] [14] [15] [47]
Omochakano
  • Phosphorus is one of the essential nutrients required for plant growth and development. It helps plants convert other nutrients in order for the plant to grow
  • Phosphorus is the "P" component of N-P-K fertilizers. The availability of soil P to plants depends on the forms of P in soils and soil pH
  • In acid soils, most plant-available P is associated with Fe and Al oxides and is best extracted with the Bray 1 extractant (0.03 M NH4F + 0.025 M HCl). The Bray 1 extractant is applicable to soils with a pH below 6.8, but not to near-neutral or alkaline soils because the acid in the extract begins to dissolve Ca phosphates. These Ca phosphates usually release only small amounts of P for plant uptake unless they begin to dissolve under more acid conditions. Generally, deficiency symptoms are not exhibited by plants growing in soils with Bray 1 levels above 15 mg/kg (Soil and Plant Analysis Council 1999)
  • In alkaline soils, most soil P is associated with Ca, either sorbed to carbonate minerals or existing as various Ca phosphate minerals, the most common of which is apatite. The Olsen (pH 8.5, 0.5 M NaHCO3) extractant was developed to measure plant-available P in alkaline soils, but it also works in many acid soils. The bicarbonate ions release P sorbed to many mineral surfaces that is plant available without dissolving the otherwise plant-unavailable P in Ca phosphates
[48] [14] [15] [47]
Potassium (K)
Ebiorokererio
  • Potassium fertilizer is sometimes called potash fertilizer
  • high potassium fertilizer contains only potassium (K) or has a high K value
  • Compost made primarily from food byproducts, especially banana peels, is an excellent source of potassium for the soil when used as a soil additive
  • Use wood ash as a light application to avoid burning plants
  • Greensand can be used as a soil additive to add potassium to the soil
  • Because potassium deficiency in plants is difficult to diagnose visually, test the soil before adding more potassium
[49] [14] [15] [47]
Omochakano
  • With all plants, potassium assists all functions within the plant. When a plant has enough potassium, it will simply be a better overall plant
  • Potassium is important to plant growth and development. Potassium helps: plants grow faster, use water better and be more drought resistant, fight off disease, resist pests, grow stronger, and produce more crops
  • K (mg/kg): > 500 = High – excellent reserve
  • 100 to 500 = Moderate – adequate levels for most plants
  • < 100 = Low – possible deficiencies
[49] [14] [15] [47]
OkonyarekanaDepthEnchera amache amachabu agosokiwaTexture Reaction - pHOrganic Carbon Conductivity - ElectricalSubsoil Cation ExchangeClay Cation ExchangeCalcium Carbonate - LimeGypsum Sodium - Exchangeable
Topsoil46.40.97124100
Subsoil46.40.411550.10
Soil Triangle - Eutric Regosols
Goteba engencho yaye - Eutric Regosols
  • A Regosol in the FAO World Reference Base for Soil Resources is very weakly developed mineral soil in unconsolidated materials. The great variation among Regosols makes it virtually impossible to give a generalised account of Regosol characteristics. The central concept of a Regosol is a deep, well-drained, medium-textured, non-differentiated mineral soil that has minimal expression of diagnostic horizons (other than an ochric surface horizon), properties or materials. Regosols occur in all climate zones without permafrost and at all elevations. Eutric indicates having a base saturation (by 1 M NH4OAc) of 50 percent or more in the major part between 20 and 100 cm from the soil surface or between 20 cm and continuous rock or a cemented or indurated layer. Regosols are particularly common in arid areas, in the dry tropics and in mountain regions. Internationally, Regosols correlate with soil taxa that are marked by incipient soil formation such as Entisols in the USDA soil taxonomy or skeletal soils in the Australian soil classification. Regosols cover an estimated 260 million hectares worldwide, mainly in arid areas in the mid-western USA, Northern Africa, the Near East and Australia. Some 50 million hectares of Regosols occur in the dry tropics and another 36 million hectares in mountain areas. Land use and management of Regosols vary widely. Some Regosols are used for capital-intensive irrigated farming but the most common land use is low volume grazing. Regosols on colluvial deposits in the loess belt of northern Europe and North America are mostly cultivated; they are planted to small grains, sugar beet and fruit trees. Regosols in mountainous regions are delicate and best left under forest
Description - Loam
  • Loams are the most useful "all around" soils; they combine the lightness and earliness of the sands, with the strength and retentiveness of the clays. Loams contain from 40 to 60 per cent, of sand, and 15 to 25 per cent, of clay. They "work up" easily, do not crust or crack, are well supplied with plant food, and, what is chiefly important, water moves through them freely and still they are not leachy. Practically all farm crops grow satisfactorily on a loam. It is especially suitable for potatoes, corn, market-gardening crops, and small fruits; but grasses, cereals, clover, alfalfa, and cotton, find it congenial. It requires no special treatment, except such attention to good tillage, drainage, and the addition of humus as is a necessary part of the best farm practice everywhere. It doesn't matter if peppers are grown in temperate, tropical or subtropical climates as long as they have a relatively dry season, so a good loam that drains well helps to offset a wetter climate. Most fruit trees live longer and produce better when they grow in balanced loam. Citrus trees like good drainage, but they need to be kept moist. Loam is a good choice for citrus
[19]
Ebimeri bia mogondo - Eutric Regosols
  • capital-intensive irrigated farming
  • small grains, sugar beet
  • fruit trees (on colluvial deposits in the loess belt of northern Europe and North America)
[52]
Metrics/Discussion
TopicEkerengoOboime bwa aman'gana
Enchera amache amachabu agosokiwa4
Omochakano
  • Soil without mottles indicates good drainage
  • Water moves through the soil readily, but not rapidly
  • Internal free-water commonly is deep or very deep
  • Water is available to plants in humid regions during much of the growing season
  • Wetness does not inhibit growth of roots for significant periods during most growing seasons
  • The soil is deep to or lacks redoximorphic features
  • A well-drained soil has "good" drainage. These soils are commonly intermediate in texture, although soils of other textural classes may also be well drained. Well-drained soils commonly retain optimum amounts of moisture for plant growth after rains or addition of irrigation water
Goteba engencho yaye
  • Drainage Class soils refers to the frequency and duration of periods when the soil is saturated with water. Alterations of the water regime by human activities, either through drainage or irrigation, are not a consideration unless they have significantly changed the morphology of the soil.

    Seven classes of natural soil drainage are recognized
    • 1. very poorly drained
    • 2. poorly drained
    • 3. somewhat poorly drained
    • 4. moderately well drained
    • 5. well drained
    • 6. somewhat excessively drained
    • 7. excessively drained
[22] [23]
Soil reference depth100 mm
Challenges
  • Soil depth limitations may affect root penetration and may constrain yield formation in roots and tubers
[9] [24]
Goteba engencho yaye
  • An approximation of actual soil depth can be derived through accounting for relevant depth limiting soil phases, obstacles to roots and occurrence of impermeable layers. Soil depth limitations which affect root penetration and may constrain yield formation (roots and tubers).

    This is a measurement in cm of reference soil depth. Reference soil depth of all soil units are set at 100 cm, except for Rendzinas and Rankers of FAO-74 and Leptosols of FAO-90, where the reference soil depth is set at 30 cm, and for Lithosols of FAO-74 and Lithic Leptosols of FAO-90, where it is set at 10 cm
[9] [25]
Base saturation79Igoro ye mia
Challenges
  • Peat moss with a pH of 3.0 can be recommended as a soil additive, but peat moss is nutrient-poor, expensive, and it's a nonrenewable resource
Ebiorokererio
  • To lower soil pH, add a source of acid, such as shredded leaves, sulfur, sawdust or peat moss
  • The ideal pH range for most crops is 6.5 to 7.0, therefore some crops may require slight pH adjustment for optimal growth
Omochakano
  • The base saturation value often shows a near linear correlation with pH
  • Base saturation = 50-80% indicates soil conditions of neutral to slightly alkaline which are ideal conditions for most crops
[9]
Goteba engencho yaye
  • The base saturation of the topsoil measures the sum of exchangeable cations (nutrients) Na, Ca, Mg and K as a percentage of the overall exchange capacity of the soil (including the same cations plus H and Al). The value often shows a near linear correlation with pH.

    Critical values as follows
    • Base Saturation < 20 % = desaturated soils, similar interpretation as extremely acid pH
    • Base Saturation of 20 – 50 % = acid conditions
    • Base Saturation of 50 – 80 % = Soil conditions of neutral to slightly alkaline which are ideal conditions for most crops
    • Base Saturation > 80% indicates saturated conditions often calcareous, sometimes sodic or saline
[9] [24]
Calcium carbonate CaCO3 - Lime0% weight
Omochakano
  • Low levels of calcium carbonate enhance soil structure and are generally beneficial for crop production
[9] [26]
Goteba engencho yaye
  • This gives the calcium carbonate (lime) content in the topsoil. Calcium carbonate is a chemical compound (a salt), with the chemical formula CaCO3. It is a common substance found as rock in all parts of the world, and is the main component of shells of marine organisms, snails, and eggshells. Calcium carbonate is the active ingredient in agricultural lime, and is usually the principal cause of hard water. It is quite common in soils particularly in drier areas and it may occur in different forms as mycelium-like threads, as soft powdery lime, as harder concretions or cemented in petrocalcic horizons.

    Low levels of calcium carbonate enhance soil structure and are generally beneficial for crop production but at higher concentrations they may induce iron deficiency and when cemented limit the water storage capacity of soils. In agronomic sense relevant limits are
    • None to very low < 2
    • Low = 2 – 5
    • Moderate = 5 – 15
    • High = 15 – 40
    • Very High > 40
[9]
Organic carbon0.97% weight
Challenges
  • Total organic carbon in mineral soils (percent): 1 to 5 = adequate levels,
  • < 1 = could indicate possible loss of organic C from erosion or other processes, particularly in temperate or colder areas
[17] [18] [9] [14] [15] [16]
Ebiorokererio
  • Increase the organic matter content by returning organic materials to soils and adding rotations with high-residue crops and deep- or dense-rooting crops
  • Ways to increase organic matter contents of soils: compost, cover crops/green manure crops, crop rotation, perennial forage crops, zero or reduced tillage, agroforestry
[17] [18] [9] [14] [15] [16]
Omochakano
  • Organic Carbon is, together with pH, the best simple indicator of the health status of the soil
  • Moderate to high soil organic carbon (SOC) in the soil is an indicator of high crop yields
  • Moderate to high amounts of organic carbon are associated with fertile soils with a good structure
[17] [18] [9] [14] [15] [16]
Goteba engencho yaye
  • This gives the percentage of organic carbon in the topsoil. Organic Carbon is, together with pH, the best simple indicator of the health status of the soil. Moderate to high amounts of organic carbon are associated with fertile soils with a good structure. Soils that are very poor in organic carbon (<0.2%), invariable need organic or inorganic fertilizer application to be productive.

    Soils with an organic matter content of less than 0.6% are considered poor in organic matter. The following classes are suggested to prepare maps of organic carbon status for mineral soils
    • Code 1 < 0.2% organic carbon
    • Code 2 = 0.2 – 0.6% organic carbon
    • Code 3 = 0.6 – 1.2% organic carbon
    • Code 4 = 1.2 – 2.0% organic carbon
    • Code 5 > 2.0% organic carbon
[9] [25]
Cation exchange capacity - clay41 cmol/kg
Challenges
  • Low CEC soils are more likely to develop potassium and magnesium (and other cation) deficiencies, while high CEC soils are less susceptible to leaching losses of these cations.. For sandy soils, the addition of a large amount of potassium at one time can lead to high losses due to leaching. This is because the potassium adds a large amount of cations at one time and soil cannot hold on to the excess potassium. Therefore, frequent additions of smaller amounts of potassium can work better to add potassium to the soil than one large amount
Ebiorokererio
  • The lower the CEC, the faster the soil pH will decrease with time
  • Sandy soils require more frequent liming than clay soils
  • The higher the CEC, the larger the quantity of lime that must be added to increase the soil pH
  • sandy soils need less lime than clay soils to increase soil pH
  • The higher the CEC, the larger the quantities of soil additives the soil will need to change soil pH, either when increasing pH with lime or high bicarbonate irrigation water, or when decreasing pH with nitrogen fertilizers or elemental sulfur
Omochakano
  • CEC in the range of 20 to 50 cmol/kg clay indicates a moderate CEC with soils containing mixed clay with kaolinite present
  • The presence of some kaolinite indicates that the soil exists in a somewhat tropical, leaching climate
  • CEC is highly dependent upon soil texture and organic matter content
  • Generally, the higher the contents of clay and organic matter in the soil, the higher the CEC
  • CEC of most soils increases with an increase in soil pH
  • Very acid soils will have high concentrations of H+ and Al3+
  • In neutral to moderately alkaline soils, Ca2+ and Mg2+ dominate
  • Poorly drained arid soils may adsorb Na in very high quantities
  • Only a small percentage of the essential plant nutrient cations (K +, Ca 2+, Mg 2+, and NH4+) will be ‘loose’ in the soil water and thus available for plant uptake, therefore the CEC is important because it provides a reservoir of nutrients
  • Cations in the soil water that are leached below the rootzone by water are replaced by cations formerly bound to the CEC
  • ‘Buffer capacity’ exists for cation nutrients as well as soil pH
  • Lighter concentrations yield white, yellow or light orange colors
  • Kaolinite has a low shrink-swell capacity and a low cation exchange capacity
Goteba engencho yaye
  • This gives the cation exchange capacity of the clay fraction in topsoil. The type of clay mineral dominantly present in the soil is often characterizes a specific set of pedogenetic factors in which the soil has developed. Tropical, leaching climates produce the clay mineral kaolinite, while confined conditions rich in Ca and Mg in climates with a pronounced dry season encourage the formation of the clay mineral smectite (montmorillonite).

    Nutrient retention capacity is of particular importance for the effectiveness of fertilizer applications and is therefore of special relevance for intermediate and high input level cropping conditions. Nutrient retention capacity refers to the capacity of the soil to retain added nutrients against losses caused by leaching. Plant nutrients are held in the soil on the exchange sites provided by the clay fraction, organic matter and the clay-humus complex. Losses vary with the intensity of leaching which is determined by the rate of drainage of soil moisture through the soil profile. Clay minerals have typical exchange capacities, with kaolinites generally having the lowest at less than 16 cmol/kg, while smectites have one of the highest with a CEC per 100g clay being 80 cmol/kg, or more. The classes generally used in the Harmonized World Soil Database are
    • Class 1 = < 20 cmol/kg clay (kaolinite dominant)
    • Class 2 = 20-50 cmol/kg clay (mixed with kaolinite present)
    • Class 3 = >50-100 cmol/kg clay (mixed, illite)
    • Class 4 = >100 cmol/kg clay (montmorillonite)
    NOTE: Soils developed on volcanic materials rich in amorphous sesquioxides may have very higher values (over 150 cmol/kg)
[9]
Cation exchange capacity - amaraba12 cmol/kg
Challenges
  • Having a larger CEC values is an indicator that the soil has a greater capacity to hold cations
  • A high CEC soil has a greater capacity to hold cations, so higher rates of fertilizer or lime are often required to change a high CEC soil
  • high CEC is an indicator that there is a high reserve of nutrients in the soil
  • Soils with low CEC can take a large amount of fertilizer or lime to correct
  • A high CEC soil requires a higher soil cation level, or soil test, to provide adequate crop nutrition
Ebiorokererio
  • The higher the CEC, the larger the quantity of lime that must be added to increase the soil pH
  • Sandy soils need less lime than clay soils to increase the pH to desired levels
  • The higher the CEC, the larger the quantities of soil additives the soil will need to change soil pH, either when increasing pH with lime or high bicarbonate irrigation water, or when decreasing pH with nitrogen fertilizers or elemental sulfur.. Acceptable saturation ranges for Soil CEC = 6-10: 3-5% K, 50-70% Ca, 8-20% Mg
Goteba engencho yaye
  • This gives the cation exchange capacity in the topsoil. The total nutrient fixing capacity of a soil is well expressed by its Cation Exchange Capacity. Soils with low CEC have little resilience and can not build up stores of nutrients. Many sandy soils have CEC less than 4 cmol/kg. The clay content, the clay type and the organic matter content all determine the total nutrient storage capacity.

    Nutrient retention capacity is of particular importance for the effectiveness of fertilizer applications and is therefore of special relevance for intermediate and high input level cropping conditions. Nutrient retention capacity refers to the capacity of the soil to retain added nutrients against losses caused by leaching. Plant nutrients are held in the soil on the exchange sites provided by the clay fraction, organic matter and the clay-humus complex. Losses vary with the intensity of leaching which is determined by the rate of drainage of soil moisture through the soil profile. Values in excess of 10 cmol/kg are considered satisfactory for most crops. This is reflected by the following code system used in the Harmonized World Soil Database
    • Code 1 = Cation Exchange Capacity < 4 cmol/kg
    • Code 2 = Cation Exchange Capacity of 4-10 cmol/kg
    • Code 3 = Cation Exchange Capacity > 10 -- 20 cmol/kg
    • Code 4 = Cation Exchange Capacity > 20 -- 40 cmol/kg
    • Code 5 = Cation Exchange Capacity > 40 cmol/kg
[9] [25]
Clay - Percent - weight19% weight
Challenges
  • Drains poorly, has few air spaces, warms slowly in spring, heavy to cultivate
  • Adverse physical properties
  • Poor workability
  • Require too much management for success in low-technology societies
  • Tree crops cannot root in the subsoil
  • Tree roots are damaged as the soil shrinks and swells
  • Low structural stability
  • Very susceptible to water erosion
Ebiorokererio
  • Do not use slopes above 5 percent for arable cropping
  • Use groundcover crops on slopes less than 5 percent
  • When terracing, use surface drainage to prevent slumping
  • Add organic matter to improve the tilth, workability, and internal drainage
  • If drainage is improved, plants can grow well in clayey soils since clay holds more nutrients than many other soils
  • Use caution when plowing and tilling
  • Do not plow excessively wet clays, or they will become cloddy
  • Till clay soils only when they are dry and crumble readily
  • In temperate climates, Plow clay soils in the fall, then leave them rough and exposed to the mellowing action of freezing and thawing
  • Frequent, shallow tillage can help to prevent crusting of the topsoil
  • Maize crops require deep cultivation and ridges in the soil to improve drainage (maize cannot tolerate waterlogging and can die if it stands in water for as long as 2 days)
  • Adding lime to clay soils can improve the soil's texture to result in looser and more porous soil
  • Use under-drainage to reduce the soil's heaviness by removing the extra water during dry periods
  • Under-drainage promotes aeration and warmth in clay soils
  • Loosen clay soils by mixing them with humus or sand
  • Barnyard manure or a green manure crop will lighten heavy clay soil
  • To lighten clay soil, spread sand on top of the clay soil and plow it under
[27] [28] [29] [2]
Omochakano
  • The feel of clay soils is slick or lumpy and sticky when very wet, and hard and smooth when dry
[3] [30]
Goteba engencho yaye
  • This measure the percentage of clay in the topsoil. Clay is naturally occurring firm earthy material, composed primarily of fine-grained (diameter less than 0.002mm) that is plastic when wet and hardens when heated and that consists primarily of hydrated silicates or aluminum. Clay is mostly composed of clay minerals which are phyllo-silicate minerals and minerals which impart plasticity and harden when fired or dried. The definition of "fine grained" used above is particles smaller than 2 µm, colloid chemists (and Eastern European soil scientists) may use 1 µm.

    The clay content of the soil is listed as a percentage (0 to 100) of the total weight of the soil. Soils is with a high percentage of clay, such as Vertisols, are used for very extensive (grazing, collection of fuelwood, and charcoal burning) through smallholder post-rainy season crop production (millet, sorghum, cotton and chickpeas) to small-scale (rice) and large-scale irrigated agriculture (cotton, wheat, barley, sorghum, chickpeas, flax, noug [Guzotia abessynica] and sugar cane). Cotton is known to perform well on Vertisols, allegedly because cotton has a vertical root system that is not damaged severely by cracking of the soil. Tree crops are generally less successful because tree roots find it difficult to establish themselves in the subsoil and are damaged as the soil shrinks and swells. Management practices for crop production should be directed primarily at water control in combination with conservation or improvement of soil fertility
[9]
Gravel - Percent - volume27% weight
Challenges
  • Gravel can affect the rooting conditions and workability of soils
  • Low in organic matter
  • Rapid drainage
  • Erosion
[9] [31] [32] [33]
Ebiorokererio
  • Add organic matter
  • fertilize regularly
  • water and mulch with manure for soft fruit, and straw for tree fruits, to overcome dry and nutrient-poor soils
  • Use terracing, the removal of stones by hand and using them as terrace fronts, to transform steep, gravelly soil into cultivable land
[9] [31] [32] [33]
Goteba engencho yaye
  • This measures the volume percentage of gravel in the topsoil. Gravel stands for the percentage of materials in a soil that are larger than 2 mm.

    Gravel can affect the rooting conditions and workability of soils. The percentage of gravel in the soil is listed on a scale of 0 to 100 percent volume
[29] [34]
Sand - Percent - weight47% weight
Challenges
  • Sand dries out rapidly and may lack nutrients because nutrients can be easily washed through the soil with rainfall or irrigation
  • low in organic matter content and native fertility
  • low in ability to retain moisture and nutrients
  • low in cation exchange and buffer capacities
  • rapidly permeable (i.e., rapid movement of water and air)
  • In the perhumid tropics, sandy soils are chemically exhausted and highly sensitive to erosion
Ebiorokererio
  • Use frequent irrigation, artificial drainage, and proper fertilization (more frequent but lower quantities of nutrients per application)
  • Total amounts of fertilizer per crop are usually quite high
  • Manage erosion and chemical exhaustion in perhumid tropical soils
  • Add organic matter to improve texture, increase water-holding capacity, and improve fertility
[35] [2] [3] [36] [37] [38]
Omochakano
  • Sand is free-draining, has a gritty feel, warms quickly, and is easy to cultivate
  • Feel is gritty, not sticky
[3]
Goteba engencho yaye
  • Sand comprises particles, or granules, ranging in diameter from 0.0625 mm (or 1/16 mm) to 2 millimeters. An individual particle in this range size is termed a sand grain. Sand feels gritty when rubbed between the fingers (silt, by comparison, feels like flour).

    This measures the percentage (0 to 100) by weight of sand in the topsoil. Sand is commonly divided into five sub-categories based on size
    • very fine sand (1/16 - 1/8 mm diameter)
    • fine sand (1/8 mm - 1/4 mm)
    • medium sand (1/4 mm - 1/2 mm)
    • coarse sand (1/2 mm - 1 mm)
    • and very coarse sand (1 mm - 2 mm)
[9] [25]
Silt - Percent - weight34% weight
Challenges
  • erosion
[39]
Ebiorokererio
  • Tillage and erosion control measures such as terracing, contour plowing, mulching and use of cover crops help to conserve the soil from compaction and serious structure deterioration
  • Fertilizers and/or lime are preconditions for continuous cultivation
[40] [41] [39]
Omochakano
  • Silty soils have a weak structure (break up easily)
  • easy to work
  • The feel of silt is smooth and soapy
  • Feel is smooth or flour-like when rubbed between the thumb and fingers
  • makes a weak ribbon (less than 2.5 cm long)
[40]
Goteba engencho yaye
  • Silt is produced by the mechanical weathering of rock, as opposed to the chemical weathering that results in clays. This mechanical weathering can be due to grinding by glaciers, eolian abrasion (sandblasting by the wind) as well as water erosion of rocks on the beds of rivers and streams. Silt is sometimes known as 'rock flour' or 'stone dust', especially when produced by glacial action. Mineralogically, silt is composed mainly of quartz and feldspar.

    This measures the percentage (0 to 100) by weight of silt in the topsoil. Soils with a lot of silt make excellent farm land, but erode easily. Erosion removes topsoil, reduces levels of soil organic matter, and contributes to the breakdown of soil structure. This creates a less favorable environment for plant growth. Soil erosion can be avoided by: maintaining a protective cover on the soil, creating a barrier to the erosive agent, modifying the landscape to control runoff amounts and rates. Specific practices to avoid water erosion: growing forage crops in rotation or as permanent cover; growing winter cover crops; interseeding; protecting the surface with crop residue; shortening the length and steepness of slopes; increasing water infiltration rates; improving aggregate stability. Specific practices to avoid wind erosion: maintaining a cover of plants or residue, planting shelterbelts, stripcropping, increase surface roughness, cultivating on the contour, maintaining soil aggregates at a size less likely to be carried by wind
[9]
Electrical conductivity0.1 dS/m
Challenges
  • inhibited uptake of water
  • irrigation and waterlogging can cause excess soil salinity
[25] [42]
Ebiorokererio
  • Control soil salinity by permitting 10-20% of the irrigation water to leach the soil, and then be drained and discharged
[25] [42]
Omochakano
  • ECe, or electrical conductivity, is a measure of soil salinity
[9]
Goteba engencho yaye
  • This gives the electrical conductivity of the topsoil. Coastal and desert soils in particular can be enriched with water-soluble salts or salts more soluble than gypsum. The salt content of a soil can be roughly estimated from the Electrical Conductivity of the soil (EC, expressed in dS/m) measured in a saturated soil paste or a more diluted suspension of soil in water.

    Accumulation of salts may cause salinity. Excess of free salts referred to as soil salinity is measured as Electric Conductivity (EC in dS/m) or as saturation of the exchange complex with sodium ions. Salinity affects crops through inhibiting the uptake of water. Moderate salinity affects growth and reduces yields; high salinity levels may kill the crop. Crops vary considerably in their resistance and response to salt in soils. Some crops will suffer at values as little as 2 dS/m (spinach) others can stand up to 16 dS/m (date palm). Agronomic relevant limits are
    • Very low ECe < 2 dS/m
    • Low ECe = 2 – 4 dS/m
    • Moderate ECe = 4 – 8 dS/m
    • High ECe = 8 – 16 dS/m
    • Very High ECe > 16 dS/m
    Some plants are more tolerant to a high salt concentration than others. Highly tolerant plants include date palm, barley, sugarbeet, cotton, asparagus, spinach
[9] [25]
Gypsum content CaSO40% volume
Ebiorokererio
  • Using water culture to increase the concentration of SO4 mixture (K2SO4 + MgSO4) increases the uptake of NO3, K, Mg and sulphur but decreases the uptake of Ca and P
  • Use soil terracing to prevent erosion
  • Use supplementary irrigation to increase productivity where water resources are available
  • Harrow the land after harvesting and before the rainy season to improve the infiltration of water and conserve soil moisture
  • Increase organic matter by replacing fallow by small-grain leguminous crops in the wheat-fallow rotations
  • Add manure
  • Use subsoiling to break the cemented gypsic subsoil to improve root penetration and reduces susceptibility to drought, especially in the case of fruit and forest trees
  • Do not mix the topsoil and subsoil
  • Apply nitrogen and phosphorus to cereals
  • N is generally applied where rainfall exceeds 260 mm annually
  • Phosphorus fertilizers increase the yield of cereals, especially under low rainfall
  • For irrigated gypsiferous soils: The use of (NH4)2CO3 solution was found to cause the optimum elimination of gypsum in gypsiferous soils with both low and high levels of gypsum; In general, there is need for ample nitrogen fertilizers for crops grown on gypsiferous soils, especially under irrigated agriculture. There are no significant differences between the requirements of crops for nitrogen on gypsiferous and non-gypsiferous soils; Molybdenum applications might benefit many plants, especially legumes
[43] [9]
Omochakano
  • Up to 2 percent gypsum in the soil favors plant growth
  • Most agricultural crops thrive in soils with no to very low gypsum content
Goteba engencho yaye
  • Calcium sulphate (gypsum) content in topsoil. Gypsum is a chemical compound (a salt) which occurs occasionally in soils particularly in the driest areas of the globe where it can occur in a flower-like form typically opaque with embedded sand grains called desert rose. In soils it may occur in fibers, crystals or soft. Research indicates that up to 2 percent gypsum in the soil favours plant growth, between 2 and 25 percent has little or no adverse effect if in powdery form, but more than 25 percent can cause substantial reduction in yields. It is suggested that reductions are due in part to imbalanced ion ratios, particularly K:Ca and Mg:Ca.

    Gypsum strongly limits available soil moisture. Tolerance of crops to gypsum varies widely (FAO, 1990; Sys, 1993). Relevant limits are considered the following
    • None to very low CaSO4 < 2%
    • Low CaSO4 = 2 – 5%
    • Moderate CaSO4 = 5 – 25%
    • High CaSO4 = 25 – 40%
    • Very High CaSO4 > 40%
Soil reaction - pH6.4 -log H+
Challenges
  • Peat moss with a pH of 3.0 can be recommended as a soil additive, but peat moss is nutrient-poor, expensive, and it's a nonrenewable resource
[4] [5] [6] [7] [8]
Ebiorokererio
  • The ideal pH range for most crops is 6.5 to 7.0, therefore some crops may require slight pH adjustment for optimal growth
  • To lower soil pH, add a source of acid, such as shredded leaves, sulfur, sawdust or peat moss
  • Add alkaline material such as limestone to decrease soil acidity
  • Apply 2.3 kg of lime per 30 square meters to raise the pH by one point
  • Applying wood ashes will raise soil pH--Wood ashes contain up to 70 percent calcium carbonate, as well as potassium, phosphorus, and many trace elements. Because it is powdery, wood ash is a fast-acting liming material
  • Limit the application of wood ashes to 1 kg per 30 square meters and only apply it every other year in the same area
  • Breed aluminum-tolerant crops
[4] [5] [6] [7]
Omochakano
  • Many plant species are adapted to acidic or alkaline soils
  • The availability of many plant nutrients (for example, P), non-essential elements (for example, Al, Cd, Pb), and essential trace elements (for example, Mn, Fe, Cu, Zn) is strongly dependent on soil pH (Miller and Gardiner 2001)
  • Generally, metal cations (for example, Mn, Fe, Ni, Cu, Zn, Cd, Pb) become more available as pH decreases, while oxyanions (for example, SO4) become more available at alkaline pH levels
  • Soil pH is strongly dependent on the chemical weathering environment. Soils in hot, humid areas and even mesic, wetter areas tend to be more acidic than those of much drier areas. Vegetation communities in those areas tend to be adapted to the soil conditions in which they developed
[9] [10] [11]
Goteba engencho yaye
  • This gives the soil reaction of subsoil. pH, measured in a soil-water solution, is a measure for the acidity and alkalinity of the soil.

    Five major pH classes are considered here that have specific agronomic significance
    • pH < 4.5 = Extremely acid soils include Acid Sulfate Soils (Mangrove soils, cat clays). Do not drain because by oxidation sulfuric acid will be produced and pH will drop lower still
    • pH 4.5 – 5.5 = Very acid soils suffering often from Al toxicity. Some crops are tolerant for these conditions (Tea, Pineapple)
    • pH 5.5 –7.2 = Acid to neutral soils - these are the best pH conditions for nutrient availability and suitable for most crops
    • pH 7.2 – 8.5 = These pH values are indicative of carbonate rich soils. Depending on the form and concentration of calcium carbonate they may result in well structured soils which may however have depth limitations when the calcium carbonate hardens in an impermeable layer and chemically forms less available carbonates affecting nutrient availability (Phosphorus, Iron)
    • pH > 8.5 = Indicates alkaline soils often highly sodic (Na reaching toxic levels), badly structured (columnar structure) and easily dispersed surface clays
[9] [44]
Exchangeable sodium1Igoro ye mia
Goteba engencho yaye
  • This gives the exchangeable sodium percentage in the topsoil. The exchangeable sodium percentage has been used to indicate levels of sodium in soils it is calculated as the ratio of Na in the CEC (or sum of cations) ESP= Na*100/CECsoil. Alternatively SAR (Sodium Adsorption Ratio) has been used (SAR= Na/Square root ((Ca+Mg)/2)) to indicate levels of sodium hazards for crops.

    Excess of free salts referred to as saturation of the exchange complex with sodium ions, which is referred to as sodicity or sodium alkalinity and is measured as Exchangeable Sodium Percentage (ESP). Sodicity causes sodium toxicity and affects soil structure leading to massive or coarse columnar structure with low permeability. Sodic soils have a low infiltration rate, they are poorly aerated and difficult to cultivate. Thus, sodic soils adversely affect the plants' growth. Agronomic relevant limits are
    • Low ESP < 6%
    • Moderate ESP = 6 – 15%
    • High ESP = 15 – 25%
    • Very High ESP > 25%
[9] [25]
Reference bulk density1.21 kg/dm3
Ebiorokererio
  • To reduce high bulk density and compaction, minimize soil disturbance and production activities when soils are wet, use designated field roads or rows for equipment traffic, reduce the number of trips across the area, and maintain or increase soil organic matter
  • Use grazing systems that minimize livestock traffic and loafing, provide protected heavy use areas, and adhere to recommended minimum grazing heights
  • Use conservation crop rotation, cover crop, deep tillage, prescribed grazing residue, and tillage management
  • Avoid plowing, timber harvesting, or compaction of the soil
[13] [14] [15] [16]
Omochakano
  • Soil bulk density may indicate soil compaction but is dependent on many soil factors including particle size distribution, soil organic matter content, and coarse fragment content
  • Bulk density increases as the sand and rock content increases
  • Bulk density decreases as the organic matter content increases
  • A mineral soil with “ideal” physical properties has 50 percent solids and 50 percent pore space occupying a given volume of space
  • At optimal water content, half the pore space is filled with water (such a soil will have a bulk density of 1.33 g/cm3)
  • Roots usually grow well in soils with bulk densities of up to 1.4 g/cm3
  • Root penetration begins to decline significantly at bulk densities above 1.7 g/cm3
  • Above 1.5 g/cm3, there is an increasing probability of adverse effects from soil compaction or high rock content
  • Coarse fragments—Soils with a coarse fragment content of > 50 percent to have a greater probability of adverse effects from infiltration rates that are too high, water storage capacity that is too low, more difficult root penetration, and greater difficulty in seed germination and seedling growth
  • A high contents of coarse fragments can limit soil productivity
[13] [14] [15] [16]
Goteba engencho yaye
  • Reference bulk density is a property of particulate materials. It is the mass of many particles of the material divided by the volume they occupy. The volume includes the space between particles as well as the space inside the pores of individual particles.

    This is a measurement in kg/dm3 of the topsoil reference bulk density. Bulk density reflects the soil’s ability to function for structural support, water and solute movement, and soil aeration. High bulk density is an indicator of low soil porosity and soil compaction. It may cause restrictions to root growth, and poor movement of air and water through the soil. Compaction can result in shallow plant rooting and poor plant growth, influencing crop yield and reducing vegetative cover available to protect soil from erosion. By reducing water infiltration into the soil, compaction can lead to increased runoff and erosion from sloping land or waterlogged soils in flatter areas. In general, some soil compaction to restrict water movement through the soil profile is beneficial under arid conditions, but under humid conditions compaction decreases yields. On cropland, long-term solutions to bulk density and soil compaction problems revolve around decreasing soil disturbance and increasing soil organic matter. A system that uses cover crops, crop residues, perennial sod, and/or reduced tillage results in increased soil organic matter, less disturbance and reduced bulk density. Additionally, the use of multi-crop systems involving plants with different rooting depths can help break up compacted soil layers
[9] [41] [45]
Nitrogen (N)
Challenges
  • Too much nitrogen in soil can harm plants
  • Adding nitrogen is easy, but removing excess nitrogen in soil is more difficult
  • Too much nitrogen in soil reduces the ability of plants to fruit and flower
[46] [14] [15] [47]
Ebiorokererio
  • Organic methods of adding nitrogen to the soil include: adding composted manure to the soil, planting a green manure crop such as borage, planting nitrogen-fixing plants such as peas or beans, and adding coffee grounds to the soil, but be careful when adding coffee grounds as this practice also creates acidity and lowers pH of the soil. Organic methods require more time than inorganic methods, but they can result in a more even distribution of the added nitrogen. Non-organic methods of adding nitrogen to the soil include the use of chemical fertilizers. A high-nitrogen fertilizer will have a high first number in the NPK ratio, for example 10-10-10. Nitrogen-containing chemical fertilizers act quickly to add nitrogen to the soil, but the nitrogen also leaves the soil quickly. If there is too much nitrogen in the soil, plant squash, cabbage, broccoli or maize which will use up large amounts of nitrogen while they grow. Note: while these plants absorb the excess nitrogen in the soil, they may look unhealthy and may produce low yields
[46] [14] [15] [47]
Omochakano
  • Total nitrogen in mineral soils (percent): > 0.5 = High – excellent reserve of nitrogen
  • 0.1 to 0.5 = Moderate – adequate levels
  • < 0.1 = Low – could indicate loss of organic N
  • Nitrogen is essential for plant growth. Plants will not grow or produce without sufficient nitrogen
  • When legumes and other nitrogen fixing plants and the bacteria called Rhizobium work together to store the nitrogen, they are creating a green warehouse in the soil. While they are growing, they release very little nitrogen into the soil, but when they are done growing and they die, their decomposition release the stored nitrogen and increases the total nitrogen in soil. Their death makes nitrogen for plants available later on. When the plant stores the nitrogen in the roots, it produces a lump on the root called a nitrogen nodule. This is harmless to the plant but very beneficial to the farm
[46] [14] [15] [47]
Phosphorus (P)
Challenges
  • Generally, it is difficult for plants to absorb phosphorus (P) so it is usually not a concern that plants will absorb too much P.: Plants grown in soils with Olsen-extractable P levels above 10 mg/kg usually will not respond to added P
  • Do not overuse P: soils with very high levels of extractable P may have a deleterious effect on water quality if such soils are subjected to erosion and the soil particles end up in receiving waters
[48] [14] [15] [47]
Ebiorokererio
  • For inorganic farms, use phosphate-containing fertilizers, such as N-P-K with a high P value (the middle value)
  • Use bone meal or rock phosphate to correct a phosphorus deficiency
  • Add compost to the soil to help plants take up the phosphorus that is already in the soil
[48] [14] [15] [47]
Omochakano
  • Phosphorus is one of the essential nutrients required for plant growth and development. It helps plants convert other nutrients in order for the plant to grow
  • Phosphorus is the "P" component of N-P-K fertilizers. The availability of soil P to plants depends on the forms of P in soils and soil pH
  • In acid soils, most plant-available P is associated with Fe and Al oxides and is best extracted with the Bray 1 extractant (0.03 M NH4F + 0.025 M HCl). The Bray 1 extractant is applicable to soils with a pH below 6.8, but not to near-neutral or alkaline soils because the acid in the extract begins to dissolve Ca phosphates. These Ca phosphates usually release only small amounts of P for plant uptake unless they begin to dissolve under more acid conditions. Generally, deficiency symptoms are not exhibited by plants growing in soils with Bray 1 levels above 15 mg/kg (Soil and Plant Analysis Council 1999)
  • In alkaline soils, most soil P is associated with Ca, either sorbed to carbonate minerals or existing as various Ca phosphate minerals, the most common of which is apatite. The Olsen (pH 8.5, 0.5 M NaHCO3) extractant was developed to measure plant-available P in alkaline soils, but it also works in many acid soils. The bicarbonate ions release P sorbed to many mineral surfaces that is plant available without dissolving the otherwise plant-unavailable P in Ca phosphates
[48] [14] [15] [47]
Potassium (K)
Ebiorokererio
  • Potassium fertilizer is sometimes called potash fertilizer
  • high potassium fertilizer contains only potassium (K) or has a high K value
  • Compost made primarily from food byproducts, especially banana peels, is an excellent source of potassium for the soil when used as a soil additive
  • Use wood ash as a light application to avoid burning plants
  • Greensand can be used as a soil additive to add potassium to the soil
  • Because potassium deficiency in plants is difficult to diagnose visually, test the soil before adding more potassium
[49] [14] [15] [47]
Omochakano
  • With all plants, potassium assists all functions within the plant. When a plant has enough potassium, it will simply be a better overall plant
  • Potassium is important to plant growth and development. Potassium helps: plants grow faster, use water better and be more drought resistant, fight off disease, resist pests, grow stronger, and produce more crops
  • K (mg/kg): > 500 = High – excellent reserve
  • 100 to 500 = Moderate – adequate levels for most plants
  • < 100 = Low – possible deficiencies
[49] [14] [15] [47]
OkonyarekanaDepthEnchera amache amachabu agosokiwaTexture Reaction - pHOrganic Carbon Conductivity - ElectricalSubsoil Cation ExchangeClay Cation ExchangeCalcium Carbonate - LimeGypsum Sodium - Exchangeable
Topsoil26.30.85103400
Subsoil26.30.4315392.40
Soil Triangle - Sodic Planosols
Goteba engencho yaye - Sodic Planosols
  • Sodic indicates having more than 15 percent exchangeable sodium or more than 50 percent exchangeable sodium plus magnesium on the exchange complex within 50 cm from the soil surface. A planosol in the FAO World Reference Base for Soil Resources is a soil with a light-coloured, coarse-textured, surface horizon that shows signs of periodic water stagnation and abruptly overlies a dense, slowly permeable subsoil with significantly more clay than the surface horizon. These soils are typically in seasonally waterlogged flat lands. They occur mainly in subtropical and temperate, semi-arid and subhumid regions. Planosols are formed mostly in clayey alluvial and colluvial deposits. Geological stratification and/or a pedogenetic process of destruction and removal of clay has resulted in the relatively coarse-textured, light-coloured surface soil abruptly overlying finer textured subsoil; impeded downward percolation of water causes temporarily reducing conditions with a stagnic colour pattern, at least close to the abrupt textural change. Planosols cover an estimated 130 million hectares of the world. Major areas with planosols occur in subtropical and temperate regions with clear alternation of wet and dry seasons, as in Latin America (southern Brazil, Paraguay and Argentina), Africa (Sahelian zone, East and Southern Africa), the east of the United States of America, Southeast Asia (Bangladesh and Thailand), and Australia
[53]
Description - Loam
  • Loams are the most useful "all around" soils; they combine the lightness and earliness of the sands, with the strength and retentiveness of the clays. Loams contain from 40 to 60 per cent, of sand, and 15 to 25 per cent, of clay. They "work up" easily, do not crust or crack, are well supplied with plant food, and, what is chiefly important, water moves through them freely and still they are not leachy. Practically all farm crops grow satisfactorily on a loam. It is especially suitable for potatoes, corn, market-gardening crops, and small fruits; but grasses, cereals, clover, alfalfa, and cotton, find it congenial. It requires no special treatment, except such attention to good tillage, drainage, and the addition of humus as is a necessary part of the best farm practice everywhere. It doesn't matter if peppers are grown in temperate, tropical or subtropical climates as long as they have a relatively dry season, so a good loam that drains well helps to offset a wetter climate. Most fruit trees live longer and produce better when they grow in balanced loam. Citrus trees like good drainage, but they need to be kept moist. Loam is a good choice for citrus
[19]
Ebimeri bia mogondo - Sodic Planosols
  • engano
  • ekemeri kebwate omori okoriegwa ogwansa
  • paddy rice (Southeast Asia)
[54] [55] [56]
Metrics/Discussion
TopicEkerengoOboime bwa aman'gana
Enchera amache amachabu agosokiwa2
Ebiorokererio
  • Artificial drainage is generally necessary for crop production
Omochakano
  • The presence of only common orange and grey mottles (10–25 percent) indicates the soil is imperfectly drained with only periodic waterlogging
  • wet at a shallow depth for significant periods during the growing season
  • Internal free-water is commonly shallow to moderately deep and transitory to permanent
  • Unless the soil is artificially drained, the growth of most mesophytic plants is restricted
  • low or very low saturated hydraulic conductivity class, or a high water table, or receives water from lateral flow, or persistent rainfall, or some combination of these factors
Goteba engencho yaye
  • Drainage Class soils refers to the frequency and duration of periods when the soil is saturated with water. Alterations of the water regime by human activities, either through drainage or irrigation, are not a consideration unless they have significantly changed the morphology of the soil.

    Seven classes of natural soil drainage are recognized
    • 1. very poorly drained
    • 2. poorly drained
    • 3. somewhat poorly drained
    • 4. moderately well drained
    • 5. well drained
    • 6. somewhat excessively drained
    • 7. excessively drained
[22] [23]
Soil reference depth100 mm
Challenges
  • Soil depth limitations may affect root penetration and may constrain yield formation in roots and tubers
[9] [24]
Goteba engencho yaye
  • An approximation of actual soil depth can be derived through accounting for relevant depth limiting soil phases, obstacles to roots and occurrence of impermeable layers. Soil depth limitations which affect root penetration and may constrain yield formation (roots and tubers).

    This is a measurement in cm of reference soil depth. Reference soil depth of all soil units are set at 100 cm, except for Rendzinas and Rankers of FAO-74 and Leptosols of FAO-90, where the reference soil depth is set at 30 cm, and for Lithosols of FAO-74 and Lithic Leptosols of FAO-90, where it is set at 10 cm
[9] [25]
Base saturation73Igoro ye mia
Challenges
  • Peat moss with a pH of 3.0 can be recommended as a soil additive, but peat moss is nutrient-poor, expensive, and it's a nonrenewable resource
Ebiorokererio
  • To lower soil pH, add a source of acid, such as shredded leaves, sulfur, sawdust or peat moss
  • The ideal pH range for most crops is 6.5 to 7.0, therefore some crops may require slight pH adjustment for optimal growth
Omochakano
  • The base saturation value often shows a near linear correlation with pH
  • Base saturation = 50-80% indicates soil conditions of neutral to slightly alkaline which are ideal conditions for most crops
[9]
Goteba engencho yaye
  • The base saturation of the topsoil measures the sum of exchangeable cations (nutrients) Na, Ca, Mg and K as a percentage of the overall exchange capacity of the soil (including the same cations plus H and Al). The value often shows a near linear correlation with pH.

    Critical values as follows
    • Base Saturation < 20 % = desaturated soils, similar interpretation as extremely acid pH
    • Base Saturation of 20 – 50 % = acid conditions
    • Base Saturation of 50 – 80 % = Soil conditions of neutral to slightly alkaline which are ideal conditions for most crops
    • Base Saturation > 80% indicates saturated conditions often calcareous, sometimes sodic or saline
[9] [24]
Calcium carbonate CaCO3 - Lime0% weight
Omochakano
  • Low levels of calcium carbonate enhance soil structure and are generally beneficial for crop production
[9] [26]
Goteba engencho yaye
  • This gives the calcium carbonate (lime) content in the topsoil. Calcium carbonate is a chemical compound (a salt), with the chemical formula CaCO3. It is a common substance found as rock in all parts of the world, and is the main component of shells of marine organisms, snails, and eggshells. Calcium carbonate is the active ingredient in agricultural lime, and is usually the principal cause of hard water. It is quite common in soils particularly in drier areas and it may occur in different forms as mycelium-like threads, as soft powdery lime, as harder concretions or cemented in petrocalcic horizons.

    Low levels of calcium carbonate enhance soil structure and are generally beneficial for crop production but at higher concentrations they may induce iron deficiency and when cemented limit the water storage capacity of soils. In agronomic sense relevant limits are
    • None to very low < 2
    • Low = 2 – 5
    • Moderate = 5 – 15
    • High = 15 – 40
    • Very High > 40
[9]
Organic carbon0.85% weight
Challenges
  • Total organic carbon in mineral soils (percent): 1 to 5 = adequate levels,
  • < 1 = could indicate possible loss of organic C from erosion or other processes, particularly in temperate or colder areas
[17] [18] [9] [14] [15] [16]
Ebiorokererio
  • Increase the organic matter content by returning organic materials to soils and adding rotations with high-residue crops and deep- or dense-rooting crops
  • Ways to increase organic matter contents of soils: compost, cover crops/green manure crops, crop rotation, perennial forage crops, zero or reduced tillage, agroforestry
[17] [18] [9] [14] [15] [16]
Omochakano
  • Organic Carbon is, together with pH, the best simple indicator of the health status of the soil
  • Moderate to high soil organic carbon (SOC) in the soil is an indicator of high crop yields
  • Moderate to high amounts of organic carbon are associated with fertile soils with a good structure
[17] [18] [9] [14] [15] [16]
Goteba engencho yaye
  • This gives the percentage of organic carbon in the topsoil. Organic Carbon is, together with pH, the best simple indicator of the health status of the soil. Moderate to high amounts of organic carbon are associated with fertile soils with a good structure. Soils that are very poor in organic carbon (<0.2%), invariable need organic or inorganic fertilizer application to be productive.

    Soils with an organic matter content of less than 0.6% are considered poor in organic matter. The following classes are suggested to prepare maps of organic carbon status for mineral soils
    • Code 1 < 0.2% organic carbon
    • Code 2 = 0.2 – 0.6% organic carbon
    • Code 3 = 0.6 – 1.2% organic carbon
    • Code 4 = 1.2 – 2.0% organic carbon
    • Code 5 > 2.0% organic carbon
[9] [25]
Cation exchange capacity - clay34 cmol/kg
Challenges
  • Low CEC soils are more likely to develop potassium and magnesium (and other cation) deficiencies, while high CEC soils are less susceptible to leaching losses of these cations.. For sandy soils, the addition of a large amount of potassium at one time can lead to high losses due to leaching. This is because the potassium adds a large amount of cations at one time and soil cannot hold on to the excess potassium. Therefore, frequent additions of smaller amounts of potassium can work better to add potassium to the soil than one large amount
Ebiorokererio
  • The lower the CEC, the faster the soil pH will decrease with time
  • Sandy soils require more frequent liming than clay soils
  • The higher the CEC, the larger the quantity of lime that must be added to increase the soil pH
  • sandy soils need less lime than clay soils to increase soil pH
  • The higher the CEC, the larger the quantities of soil additives the soil will need to change soil pH, either when increasing pH with lime or high bicarbonate irrigation water, or when decreasing pH with nitrogen fertilizers or elemental sulfur
Omochakano
  • CEC in the range of 20 to 50 cmol/kg clay indicates a moderate CEC with soils containing mixed clay with kaolinite present
  • The presence of some kaolinite indicates that the soil exists in a somewhat tropical, leaching climate
  • CEC is highly dependent upon soil texture and organic matter content
  • Generally, the higher the contents of clay and organic matter in the soil, the higher the CEC
  • CEC of most soils increases with an increase in soil pH
  • Very acid soils will have high concentrations of H+ and Al3+
  • In neutral to moderately alkaline soils, Ca2+ and Mg2+ dominate
  • Poorly drained arid soils may adsorb Na in very high quantities
  • Only a small percentage of the essential plant nutrient cations (K +, Ca 2+, Mg 2+, and NH4+) will be ‘loose’ in the soil water and thus available for plant uptake, therefore the CEC is important because it provides a reservoir of nutrients
  • Cations in the soil water that are leached below the rootzone by water are replaced by cations formerly bound to the CEC
  • ‘Buffer capacity’ exists for cation nutrients as well as soil pH
  • Lighter concentrations yield white, yellow or light orange colors
  • Kaolinite has a low shrink-swell capacity and a low cation exchange capacity
Goteba engencho yaye
  • This gives the cation exchange capacity of the clay fraction in topsoil. The type of clay mineral dominantly present in the soil is often characterizes a specific set of pedogenetic factors in which the soil has developed. Tropical, leaching climates produce the clay mineral kaolinite, while confined conditions rich in Ca and Mg in climates with a pronounced dry season encourage the formation of the clay mineral smectite (montmorillonite).

    Nutrient retention capacity is of particular importance for the effectiveness of fertilizer applications and is therefore of special relevance for intermediate and high input level cropping conditions. Nutrient retention capacity refers to the capacity of the soil to retain added nutrients against losses caused by leaching. Plant nutrients are held in the soil on the exchange sites provided by the clay fraction, organic matter and the clay-humus complex. Losses vary with the intensity of leaching which is determined by the rate of drainage of soil moisture through the soil profile. Clay minerals have typical exchange capacities, with kaolinites generally having the lowest at less than 16 cmol/kg, while smectites have one of the highest with a CEC per 100g clay being 80 cmol/kg, or more. The classes generally used in the Harmonized World Soil Database are
    • Class 1 = < 20 cmol/kg clay (kaolinite dominant)
    • Class 2 = 20-50 cmol/kg clay (mixed with kaolinite present)
    • Class 3 = >50-100 cmol/kg clay (mixed, illite)
    • Class 4 = >100 cmol/kg clay (montmorillonite)
    NOTE: Soils developed on volcanic materials rich in amorphous sesquioxides may have very higher values (over 150 cmol/kg)
[9]
Cation exchange capacity - amaraba10 cmol/kg
Challenges
  • Having a larger CEC values is an indicator that the soil has a greater capacity to hold cations
  • A high CEC soil has a greater capacity to hold cations, so higher rates of fertilizer or lime are often required to change a high CEC soil
  • high CEC is an indicator that there is a high reserve of nutrients in the soil
  • Soils with low CEC can take a large amount of fertilizer or lime to correct
  • A high CEC soil requires a higher soil cation level, or soil test, to provide adequate crop nutrition
Ebiorokererio
  • The higher the CEC, the larger the quantity of lime that must be added to increase the soil pH
  • Sandy soils need less lime than clay soils to increase the pH to desired levels
  • The higher the CEC, the larger the quantities of soil additives the soil will need to change soil pH, either when increasing pH with lime or high bicarbonate irrigation water, or when decreasing pH with nitrogen fertilizers or elemental sulfur.. Acceptable saturation ranges for Soil CEC = 6-10: 3-5% K, 50-70% Ca, 8-20% Mg
Goteba engencho yaye
  • This gives the cation exchange capacity in the topsoil. The total nutrient fixing capacity of a soil is well expressed by its Cation Exchange Capacity. Soils with low CEC have little resilience and can not build up stores of nutrients. Many sandy soils have CEC less than 4 cmol/kg. The clay content, the clay type and the organic matter content all determine the total nutrient storage capacity.

    Nutrient retention capacity is of particular importance for the effectiveness of fertilizer applications and is therefore of special relevance for intermediate and high input level cropping conditions. Nutrient retention capacity refers to the capacity of the soil to retain added nutrients against losses caused by leaching. Plant nutrients are held in the soil on the exchange sites provided by the clay fraction, organic matter and the clay-humus complex. Losses vary with the intensity of leaching which is determined by the rate of drainage of soil moisture through the soil profile. Values in excess of 10 cmol/kg are considered satisfactory for most crops. This is reflected by the following code system used in the Harmonized World Soil Database
    • Code 1 = Cation Exchange Capacity < 4 cmol/kg
    • Code 2 = Cation Exchange Capacity of 4-10 cmol/kg
    • Code 3 = Cation Exchange Capacity > 10 -- 20 cmol/kg
    • Code 4 = Cation Exchange Capacity > 20 -- 40 cmol/kg
    • Code 5 = Cation Exchange Capacity > 40 cmol/kg
[9] [25]
Clay - Percent - weight24% weight
Challenges
  • Drains poorly, has few air spaces, warms slowly in spring, heavy to cultivate
  • Adverse physical properties
  • Poor workability
  • Require too much management for success in low-technology societies
  • Tree crops cannot root in the subsoil
  • Tree roots are damaged as the soil shrinks and swells
  • Low structural stability
  • Very susceptible to water erosion
Ebiorokererio
  • Do not use slopes above 5 percent for arable cropping
  • Use groundcover crops on slopes less than 5 percent
  • When terracing, use surface drainage to prevent slumping
  • Add organic matter to improve the tilth, workability, and internal drainage
  • If drainage is improved, plants can grow well in clayey soils since clay holds more nutrients than many other soils
  • Use caution when plowing and tilling
  • Do not plow excessively wet clays, or they will become cloddy
  • Till clay soils only when they are dry and crumble readily
  • In temperate climates, Plow clay soils in the fall, then leave them rough and exposed to the mellowing action of freezing and thawing
  • Frequent, shallow tillage can help to prevent crusting of the topsoil
  • Maize crops require deep cultivation and ridges in the soil to improve drainage (maize cannot tolerate waterlogging and can die if it stands in water for as long as 2 days)
  • Adding lime to clay soils can improve the soil's texture to result in looser and more porous soil
  • Use under-drainage to reduce the soil's heaviness by removing the extra water during dry periods
  • Under-drainage promotes aeration and warmth in clay soils
  • Loosen clay soils by mixing them with humus or sand
  • Barnyard manure or a green manure crop will lighten heavy clay soil
  • To lighten clay soil, spread sand on top of the clay soil and plow it under
[27] [28] [29] [2]
Omochakano
  • The feel of clay soils is slick or lumpy and sticky when very wet, and hard and smooth when dry
[3] [30]
Goteba engencho yaye
  • This measure the percentage of clay in the topsoil. Clay is naturally occurring firm earthy material, composed primarily of fine-grained (diameter less than 0.002mm) that is plastic when wet and hardens when heated and that consists primarily of hydrated silicates or aluminum. Clay is mostly composed of clay minerals which are phyllo-silicate minerals and minerals which impart plasticity and harden when fired or dried. The definition of "fine grained" used above is particles smaller than 2 µm, colloid chemists (and Eastern European soil scientists) may use 1 µm.

    The clay content of the soil is listed as a percentage (0 to 100) of the total weight of the soil. Soils is with a high percentage of clay, such as Vertisols, are used for very extensive (grazing, collection of fuelwood, and charcoal burning) through smallholder post-rainy season crop production (millet, sorghum, cotton and chickpeas) to small-scale (rice) and large-scale irrigated agriculture (cotton, wheat, barley, sorghum, chickpeas, flax, noug [Guzotia abessynica] and sugar cane). Cotton is known to perform well on Vertisols, allegedly because cotton has a vertical root system that is not damaged severely by cracking of the soil. Tree crops are generally less successful because tree roots find it difficult to establish themselves in the subsoil and are damaged as the soil shrinks and swells. Management practices for crop production should be directed primarily at water control in combination with conservation or improvement of soil fertility
[9]
Gravel - Percent - volume4% weight
Challenges
  • Gravel can affect the rooting conditions and workability of soils
  • May be low in organic matter
[9] [31] [32] [33]
Ebiorokererio
  • Add organic matter
  • fertilize regularly
  • Use pea gravel as a mulch to protect the roots of herbs and other drought-tolerant plants
  • Pea gravel reflects heat and provides good drainage
[9] [31] [32] [33]
Goteba engencho yaye
  • This measures the volume percentage of gravel in the topsoil. Gravel stands for the percentage of materials in a soil that are larger than 2 mm.

    Gravel can affect the rooting conditions and workability of soils. The percentage of gravel in the soil is listed on a scale of 0 to 100 percent volume
[29] [34]
Sand - Percent - weight41% weight
Challenges
  • Sand dries out rapidly and may lack nutrients because nutrients can be easily washed through the soil with rainfall or irrigation
  • low in organic matter content and native fertility
  • low in ability to retain moisture and nutrients
  • low in cation exchange and buffer capacities
  • rapidly permeable (i.e., rapid movement of water and air)
  • In the perhumid tropics, sandy soils are chemically exhausted and highly sensitive to erosion
Ebiorokererio
  • Use frequent irrigation, artificial drainage, and proper fertilization (more frequent but lower quantities of nutrients per application)
  • Total amounts of fertilizer per crop are usually quite high
  • Manage erosion and chemical exhaustion in perhumid tropical soils
  • Add organic matter to improve texture, increase water-holding capacity, and improve fertility
[35] [2] [3] [36] [37] [38]
Omochakano
  • Sand is free-draining, has a gritty feel, warms quickly, and is easy to cultivate
  • Feel is gritty, not sticky
[3]
Goteba engencho yaye
  • Sand comprises particles, or granules, ranging in diameter from 0.0625 mm (or 1/16 mm) to 2 millimeters. An individual particle in this range size is termed a sand grain. Sand feels gritty when rubbed between the fingers (silt, by comparison, feels like flour).

    This measures the percentage (0 to 100) by weight of sand in the topsoil. Sand is commonly divided into five sub-categories based on size
    • very fine sand (1/16 - 1/8 mm diameter)
    • fine sand (1/8 mm - 1/4 mm)
    • medium sand (1/4 mm - 1/2 mm)
    • coarse sand (1/2 mm - 1 mm)
    • and very coarse sand (1 mm - 2 mm)
[9] [25]
Silt - Percent - weight35% weight
Challenges
  • erosion
[39]
Ebiorokererio
  • Tillage and erosion control measures such as terracing, contour plowing, mulching and use of cover crops help to conserve the soil from compaction and serious structure deterioration
  • Fertilizers and/or lime are preconditions for continuous cultivation
[40] [41] [39]
Omochakano
  • Silty soils have a weak structure (break up easily)
  • easy to work
  • The feel of silt is smooth and soapy
  • Feel is smooth or flour-like when rubbed between the thumb and fingers
  • makes a weak ribbon (less than 2.5 cm long)
[40]
Goteba engencho yaye
  • Silt is produced by the mechanical weathering of rock, as opposed to the chemical weathering that results in clays. This mechanical weathering can be due to grinding by glaciers, eolian abrasion (sandblasting by the wind) as well as water erosion of rocks on the beds of rivers and streams. Silt is sometimes known as 'rock flour' or 'stone dust', especially when produced by glacial action. Mineralogically, silt is composed mainly of quartz and feldspar.

    This measures the percentage (0 to 100) by weight of silt in the topsoil. Soils with a lot of silt make excellent farm land, but erode easily. Erosion removes topsoil, reduces levels of soil organic matter, and contributes to the breakdown of soil structure. This creates a less favorable environment for plant growth. Soil erosion can be avoided by: maintaining a protective cover on the soil, creating a barrier to the erosive agent, modifying the landscape to control runoff amounts and rates. Specific practices to avoid water erosion: growing forage crops in rotation or as permanent cover; growing winter cover crops; interseeding; protecting the surface with crop residue; shortening the length and steepness of slopes; increasing water infiltration rates; improving aggregate stability. Specific practices to avoid wind erosion: maintaining a cover of plants or residue, planting shelterbelts, stripcropping, increase surface roughness, cultivating on the contour, maintaining soil aggregates at a size less likely to be carried by wind
[9]
Electrical conductivity0.1 dS/m
Challenges
  • inhibited uptake of water
  • irrigation and waterlogging can cause excess soil salinity
[25] [42]
Ebiorokererio
  • Control soil salinity by permitting 10-20% of the irrigation water to leach the soil, and then be drained and discharged
[25] [42]
Omochakano
  • ECe, or electrical conductivity, is a measure of soil salinity
[9]
Goteba engencho yaye
  • This gives the electrical conductivity of the topsoil. Coastal and desert soils in particular can be enriched with water-soluble salts or salts more soluble than gypsum. The salt content of a soil can be roughly estimated from the Electrical Conductivity of the soil (EC, expressed in dS/m) measured in a saturated soil paste or a more diluted suspension of soil in water.

    Accumulation of salts may cause salinity. Excess of free salts referred to as soil salinity is measured as Electric Conductivity (EC in dS/m) or as saturation of the exchange complex with sodium ions. Salinity affects crops through inhibiting the uptake of water. Moderate salinity affects growth and reduces yields; high salinity levels may kill the crop. Crops vary considerably in their resistance and response to salt in soils. Some crops will suffer at values as little as 2 dS/m (spinach) others can stand up to 16 dS/m (date palm). Agronomic relevant limits are
    • Very low ECe < 2 dS/m
    • Low ECe = 2 – 4 dS/m
    • Moderate ECe = 4 – 8 dS/m
    • High ECe = 8 – 16 dS/m
    • Very High ECe > 16 dS/m
    Some plants are more tolerant to a high salt concentration than others. Highly tolerant plants include date palm, barley, sugarbeet, cotton, asparagus, spinach
[9] [25]
Gypsum content CaSO40% volume
Ebiorokererio
  • Using water culture to increase the concentration of SO4 mixture (K2SO4 + MgSO4) increases the uptake of NO3, K, Mg and sulphur but decreases the uptake of Ca and P
  • Use soil terracing to prevent erosion
  • Use supplementary irrigation to increase productivity where water resources are available
  • Harrow the land after harvesting and before the rainy season to improve the infiltration of water and conserve soil moisture
  • Increase organic matter by replacing fallow by small-grain leguminous crops in the wheat-fallow rotations
  • Add manure
  • Use subsoiling to break the cemented gypsic subsoil to improve root penetration and reduces susceptibility to drought, especially in the case of fruit and forest trees
  • Do not mix the topsoil and subsoil
  • Apply nitrogen and phosphorus to cereals
  • N is generally applied where rainfall exceeds 260 mm annually
  • Phosphorus fertilizers increase the yield of cereals, especially under low rainfall
  • For irrigated gypsiferous soils: The use of (NH4)2CO3 solution was found to cause the optimum elimination of gypsum in gypsiferous soils with both low and high levels of gypsum; In general, there is need for ample nitrogen fertilizers for crops grown on gypsiferous soils, especially under irrigated agriculture. There are no significant differences between the requirements of crops for nitrogen on gypsiferous and non-gypsiferous soils; Molybdenum applications might benefit many plants, especially legumes
[43] [9]
Omochakano
  • Up to 2 percent gypsum in the soil favors plant growth
  • Most agricultural crops thrive in soils with no to very low gypsum content
Goteba engencho yaye
  • Calcium sulphate (gypsum) content in topsoil. Gypsum is a chemical compound (a salt) which occurs occasionally in soils particularly in the driest areas of the globe where it can occur in a flower-like form typically opaque with embedded sand grains called desert rose. In soils it may occur in fibers, crystals or soft. Research indicates that up to 2 percent gypsum in the soil favours plant growth, between 2 and 25 percent has little or no adverse effect if in powdery form, but more than 25 percent can cause substantial reduction in yields. It is suggested that reductions are due in part to imbalanced ion ratios, particularly K:Ca and Mg:Ca.

    Gypsum strongly limits available soil moisture. Tolerance of crops to gypsum varies widely (FAO, 1990; Sys, 1993). Relevant limits are considered the following
    • None to very low CaSO4 < 2%
    • Low CaSO4 = 2 – 5%
    • Moderate CaSO4 = 5 – 25%
    • High CaSO4 = 25 – 40%
    • Very High CaSO4 > 40%
Soil reaction - pH6.3 -log H+
Challenges
  • Peat moss with a pH of 3.0 can be recommended as a soil additive, but peat moss is nutrient-poor, expensive, and it's a nonrenewable resource
[4] [5] [6] [7] [8]
Ebiorokererio
  • The ideal pH range for most crops is 6.5 to 7.0, therefore some crops may require slight pH adjustment for optimal growth
  • To lower soil pH, add a source of acid, such as shredded leaves, sulfur, sawdust or peat moss
  • Add alkaline material such as limestone to decrease soil acidity
  • Apply 2.3 kg of lime per 30 square meters to raise the pH by one point
  • Applying wood ashes will raise soil pH--Wood ashes contain up to 70 percent calcium carbonate, as well as potassium, phosphorus, and many trace elements. Because it is powdery, wood ash is a fast-acting liming material
  • Limit the application of wood ashes to 1 kg per 30 square meters and only apply it every other year in the same area
  • Breed aluminum-tolerant crops
[4] [5] [6] [7]
Omochakano
  • Many plant species are adapted to acidic or alkaline soils
  • The availability of many plant nutrients (for example, P), non-essential elements (for example, Al, Cd, Pb), and essential trace elements (for example, Mn, Fe, Cu, Zn) is strongly dependent on soil pH (Miller and Gardiner 2001)
  • Generally, metal cations (for example, Mn, Fe, Ni, Cu, Zn, Cd, Pb) become more available as pH decreases, while oxyanions (for example, SO4) become more available at alkaline pH levels
  • Soil pH is strongly dependent on the chemical weathering environment. Soils in hot, humid areas and even mesic, wetter areas tend to be more acidic than those of much drier areas. Vegetation communities in those areas tend to be adapted to the soil conditions in which they developed
[9] [10] [11]
Goteba engencho yaye
  • This gives the soil reaction of subsoil. pH, measured in a soil-water solution, is a measure for the acidity and alkalinity of the soil.

    Five major pH classes are considered here that have specific agronomic significance
    • pH < 4.5 = Extremely acid soils include Acid Sulfate Soils (Mangrove soils, cat clays). Do not drain because by oxidation sulfuric acid will be produced and pH will drop lower still
    • pH 4.5 – 5.5 = Very acid soils suffering often from Al toxicity. Some crops are tolerant for these conditions (Tea, Pineapple)
    • pH 5.5 –7.2 = Acid to neutral soils - these are the best pH conditions for nutrient availability and suitable for most crops
    • pH 7.2 – 8.5 = These pH values are indicative of carbonate rich soils. Depending on the form and concentration of calcium carbonate they may result in well structured soils which may however have depth limitations when the calcium carbonate hardens in an impermeable layer and chemically forms less available carbonates affecting nutrient availability (Phosphorus, Iron)
    • pH > 8.5 = Indicates alkaline soils often highly sodic (Na reaching toxic levels), badly structured (columnar structure) and easily dispersed surface clays
[9] [44]
Exchangeable sodium5Igoro ye mia
Challenges
  • Sodicity causes sodium toxicity and affects soil structure leading to massive or coarse columnar structure with low permeability to water and roots
  • low infiltration rate
  • poorly aerated
  • difficult to cultivate
  • sodic soils can adversely affect plant growth
  • high pH lowers availability of some essential plant nutrients, such as calcium, magnesium, P, Fe, Mn, and Zn
  • risk of toxic levels of sodium, molybdenum, and boron
Goteba engencho yaye
  • This gives the exchangeable sodium percentage in the topsoil. The exchangeable sodium percentage has been used to indicate levels of sodium in soils it is calculated as the ratio of Na in the CEC (or sum of cations) ESP= Na*100/CECsoil. Alternatively SAR (Sodium Adsorption Ratio) has been used (SAR= Na/Square root ((Ca+Mg)/2)) to indicate levels of sodium hazards for crops.

    Excess of free salts referred to as saturation of the exchange complex with sodium ions, which is referred to as sodicity or sodium alkalinity and is measured as Exchangeable Sodium Percentage (ESP). Sodicity causes sodium toxicity and affects soil structure leading to massive or coarse columnar structure with low permeability. Sodic soils have a low infiltration rate, they are poorly aerated and difficult to cultivate. Thus, sodic soils adversely affect the plants' growth. Agronomic relevant limits are
    • Low ESP < 6%
    • Moderate ESP = 6 – 15%
    • High ESP = 15 – 25%
    • Very High ESP > 25%
[9] [25]
Reference bulk density1.38 kg/dm3
Ebiorokererio
  • To reduce high bulk density and compaction, minimize soil disturbance and production activities when soils are wet, use designated field roads or rows for equipment traffic, reduce the number of trips across the area, and maintain or increase soil organic matter
  • Use grazing systems that minimize livestock traffic and loafing, provide protected heavy use areas, and adhere to recommended minimum grazing heights
  • Use conservation crop rotation, cover crop, deep tillage, prescribed grazing residue, and tillage management
  • Avoid plowing, timber harvesting, or compaction of the soil
[13] [14] [15] [16]
Omochakano
  • Soil bulk density may indicate soil compaction but is dependent on many soil factors including particle size distribution, soil organic matter content, and coarse fragment content
  • Bulk density increases as the sand and rock content increases
  • Bulk density decreases as the organic matter content increases
  • A mineral soil with “ideal” physical properties has 50 percent solids and 50 percent pore space occupying a given volume of space
  • At optimal water content, half the pore space is filled with water (such a soil will have a bulk density of 1.33 g/cm3)
  • Roots usually grow well in soils with bulk densities of up to 1.4 g/cm3
  • Root penetration begins to decline significantly at bulk densities above 1.7 g/cm3
  • Above 1.5 g/cm3, there is an increasing probability of adverse effects from soil compaction or high rock content
  • Coarse fragments—Soils with a coarse fragment content of > 50 percent to have a greater probability of adverse effects from infiltration rates that are too high, water storage capacity that is too low, more difficult root penetration, and greater difficulty in seed germination and seedling growth
  • A high contents of coarse fragments can limit soil productivity
[13] [14] [15] [16]
Goteba engencho yaye
  • Reference bulk density is a property of particulate materials. It is the mass of many particles of the material divided by the volume they occupy. The volume includes the space between particles as well as the space inside the pores of individual particles.

    This is a measurement in kg/dm3 of the topsoil reference bulk density. Bulk density reflects the soil’s ability to function for structural support, water and solute movement, and soil aeration. High bulk density is an indicator of low soil porosity and soil compaction. It may cause restrictions to root growth, and poor movement of air and water through the soil. Compaction can result in shallow plant rooting and poor plant growth, influencing crop yield and reducing vegetative cover available to protect soil from erosion. By reducing water infiltration into the soil, compaction can lead to increased runoff and erosion from sloping land or waterlogged soils in flatter areas. In general, some soil compaction to restrict water movement through the soil profile is beneficial under arid conditions, but under humid conditions compaction decreases yields. On cropland, long-term solutions to bulk density and soil compaction problems revolve around decreasing soil disturbance and increasing soil organic matter. A system that uses cover crops, crop residues, perennial sod, and/or reduced tillage results in increased soil organic matter, less disturbance and reduced bulk density. Additionally, the use of multi-crop systems involving plants with different rooting depths can help break up compacted soil layers
[9] [41] [45]
Nitrogen (N)
Challenges
  • Too much nitrogen in soil can harm plants
  • Adding nitrogen is easy, but removing excess nitrogen in soil is more difficult
  • Too much nitrogen in soil reduces the ability of plants to fruit and flower
[46] [14] [15] [47]
Ebiorokererio
  • Organic methods of adding nitrogen to the soil include: adding composted manure to the soil, planting a green manure crop such as borage, planting nitrogen-fixing plants such as peas or beans, and adding coffee grounds to the soil, but be careful when adding coffee grounds as this practice also creates acidity and lowers pH of the soil. Organic methods require more time than inorganic methods, but they can result in a more even distribution of the added nitrogen. Non-organic methods of adding nitrogen to the soil include the use of chemical fertilizers. A high-nitrogen fertilizer will have a high first number in the NPK ratio, for example 10-10-10. Nitrogen-containing chemical fertilizers act quickly to add nitrogen to the soil, but the nitrogen also leaves the soil quickly. If there is too much nitrogen in the soil, plant squash, cabbage, broccoli or maize which will use up large amounts of nitrogen while they grow. Note: while these plants absorb the excess nitrogen in the soil, they may look unhealthy and may produce low yields
[46] [14] [15] [47]
Omochakano
  • Total nitrogen in mineral soils (percent): > 0.5 = High – excellent reserve of nitrogen
  • 0.1 to 0.5 = Moderate – adequate levels
  • < 0.1 = Low – could indicate loss of organic N
  • Nitrogen is essential for plant growth. Plants will not grow or produce without sufficient nitrogen
  • When legumes and other nitrogen fixing plants and the bacteria called Rhizobium work together to store the nitrogen, they are creating a green warehouse in the soil. While they are growing, they release very little nitrogen into the soil, but when they are done growing and they die, their decomposition release the stored nitrogen and increases the total nitrogen in soil. Their death makes nitrogen for plants available later on. When the plant stores the nitrogen in the roots, it produces a lump on the root called a nitrogen nodule. This is harmless to the plant but very beneficial to the farm
[46] [14] [15] [47]
Phosphorus (P)
Challenges
  • Generally, it is difficult for plants to absorb phosphorus (P) so it is usually not a concern that plants will absorb too much P.: Plants grown in soils with Olsen-extractable P levels above 10 mg/kg usually will not respond to added P
  • Do not overuse P: soils with very high levels of extractable P may have a deleterious effect on water quality if such soils are subjected to erosion and the soil particles end up in receiving waters
[48] [14] [15] [47]
Ebiorokererio
  • For inorganic farms, use phosphate-containing fertilizers, such as N-P-K with a high P value (the middle value)
  • Use bone meal or rock phosphate to correct a phosphorus deficiency
  • Add compost to the soil to help plants take up the phosphorus that is already in the soil
[48] [14] [15] [47]
Omochakano
  • Phosphorus is one of the essential nutrients required for plant growth and development. It helps plants convert other nutrients in order for the plant to grow
  • Phosphorus is the "P" component of N-P-K fertilizers. The availability of soil P to plants depends on the forms of P in soils and soil pH
  • In acid soils, most plant-available P is associated with Fe and Al oxides and is best extracted with the Bray 1 extractant (0.03 M NH4F + 0.025 M HCl). The Bray 1 extractant is applicable to soils with a pH below 6.8, but not to near-neutral or alkaline soils because the acid in the extract begins to dissolve Ca phosphates. These Ca phosphates usually release only small amounts of P for plant uptake unless they begin to dissolve under more acid conditions. Generally, deficiency symptoms are not exhibited by plants growing in soils with Bray 1 levels above 15 mg/kg (Soil and Plant Analysis Council 1999)
  • In alkaline soils, most soil P is associated with Ca, either sorbed to carbonate minerals or existing as various Ca phosphate minerals, the most common of which is apatite. The Olsen (pH 8.5, 0.5 M NaHCO3) extractant was developed to measure plant-available P in alkaline soils, but it also works in many acid soils. The bicarbonate ions release P sorbed to many mineral surfaces that is plant available without dissolving the otherwise plant-unavailable P in Ca phosphates
[48] [14] [15] [47]
Potassium (K)
Ebiorokererio
  • Potassium fertilizer is sometimes called potash fertilizer
  • high potassium fertilizer contains only potassium (K) or has a high K value
  • Compost made primarily from food byproducts, especially banana peels, is an excellent source of potassium for the soil when used as a soil additive
  • Use wood ash as a light application to avoid burning plants
  • Greensand can be used as a soil additive to add potassium to the soil
  • Because potassium deficiency in plants is difficult to diagnose visually, test the soil before adding more potassium
[49] [14] [15] [47]
Omochakano
  • With all plants, potassium assists all functions within the plant. When a plant has enough potassium, it will simply be a better overall plant
  • Potassium is important to plant growth and development. Potassium helps: plants grow faster, use water better and be more drought resistant, fight off disease, resist pests, grow stronger, and produce more crops
  • K (mg/kg): > 500 = High – excellent reserve
  • 100 to 500 = Moderate – adequate levels for most plants
  • < 100 = Low – possible deficiencies
[49] [14] [15] [47]
Zero Tillage

Conservation tillage systems such as zero tillage cause minimum disturbance to the soil after the previous crop has been harvested. In zero tillage, the ideal is to plant direct into the soil, without hoeing or plowing. Tillage is reduced to ripping planting lines or making holes for planting with a hoe. Crop residues are left in the field to reduce soil erosion, conserve moisture, inhibit weed growth, and act as green manure. Zero tillage is not recommended when disease is present. To manage disease, crop residues must be either removed from the field and destroyed or deeply ploughed to reduce sources of disease infection and spread.


Advantages of conservation tillage include less machinery, labour and fuel, as well as reduced soil erosion and compaction. Disadvantages of conservation tillage include lower soil temperatures, slower germination and emergence when direct sowing is used, slower early growth, delayed competition with weeds, higher incidence of root diseases, heavier crop residue, the possibility of more difficult planter operation, weed spectrum changes, and potential increase of soil insect pests or insects that spend part of their life cycle in the soil (e.g. cutworms, thrips, leafmining flies, grubs). Cultivation exposes these pests to desiccation by the sun heat and to predation by natural enemies.


Green Manuring

Green manure legumes create nitrogen in the soil by fixing it from the atmosphere.


Benefits of Green Manure Cover Crops

  • Easy to grow
  • Increases soil organic matter
  • Reduce soil losses from wind and water erosion
  • If it is a legume, it can fix nitrogen. When the legume is mature, chopped up and added to the soil, it will add nitrogen to the soil which will be used by later crops on the land.
  • The roots of the green manure crops extract nutrients from deep in the soil.
  • The deep roots work to break up and aerate the soil
  • When the green manure is added to the soil, it works to lighten and loosen the soil to aerate and improve drainage, making the soil healthier for later crops. After tilling in a green manure crop, we see the soil level in the farm beds raise several inches. The soil is loose and no longer compacted.
  • Green manure crops include jack beans, perennial peanut, and Mucuna.
  • These plants help the main crop by increasing soil fertility by adding nitrogen to the soil by nitrogen fixation.
  • They add biomass (organic matter) to the soil.
  • As cover crops, they reduce soil loss.

Planting Green Manure Crops

Green manure crops can be planting using intercropping with the main crop or by using crop rotation in which the green manure crop is planted in-between plantings of the main crop. For intercropping, plant the legume seeds in rows between rows of the main crop. Plow the legumes into the soil at the start of the rainy season.


In crop rotation, plant legumes after the main crop has been harvested. The legumes will benefit the field as a cover crop and as green manure. At full biomass maturity, plow the legumes into the soil as green manure for the next crop.


For a source of green manure to the field, cut the legumes at full maturity, shred, and spread over the field.


Preventing Soil Erosion while Adding Nutrients to the Soil

The first step in soil management is preventing the loss, or erosion, of soil. Topsoil is particularly vulnerable to erosion if not protected by plants or mulch or by other measures. The soil that remains after the loss of topsoil is usually less productive, which can result in lower yields. The challenge is to protect soil while using the land for food production and other non-food activities.


Soil erosion is caused mainly by wind and water but also by incorrect cultivation practices. Rain and wind dislodge and then carry away soil particles. Where the soil is bare or the vegetation poor, rainwater does not seep into the soil; instead it runs off and carries with it loose topsoil. Sloping land and light soils with low organic matter content are both prone to erosion. Once eroded, the soil is lost forever.


Soil erosion is a problem in regions with little vegetation, particularly in the semi-arid and arid zones. In the humid tropics, erosion was not considered a problem when the land was in its natural state, because the variety of native plants kept the soils covered at all times. Now, people are clearing more land for agricultural purposes, and the situation has changed. Heavy rains coupled with poor soil management of cultivated areas are now common causes of soil erosion in the humid areas.


Water Erosion

Some common forms of water erosion include:

  • Sheet erosion: a thin top layer of soil is removed from the soil by the impact of rain. With sheet erosion, small heaps of loose material (e.g. grass) amass between fine lines of sand after a rainstorm. This erosion takes place across a whole garden or field.
  • Rill erosion: water flows over minor depressions on the land's surface and cuts small channels into the soil. The erosion takes place along the length of these channels.
  • Gully erosion: a gully forms along natural depressions on the soil's surface or on slopes. The head of a gully moves up the slope in the opposite direction of the flow of water. Gullies are symptoms of severe erosion.

Wind Erosion

This occurs mostly on light soils and bare land. High winds cause severe damage. Wind erosion is a common problem in dry and semi-arid areas, as well as in areas that get seasonal rains.


Unlike water which only erodes on slopes, wind can remove soil from flat land as well as from sloping land; it can also transport the soil particles through the air and deposit them far away. Soils vulnerable to wind erosion are dry, loose, light soils with little or no vegetative cover.


Plowing up and down a slope causes soil erosion. To prevent the loss of soils, certain measures must be taken.


These include:

  • clearing only the land to be cultivated;
  • planting along a contour and using grassed channels;
  • establishing windbreaks and bench terraces;
  • plowing along a contour;
  • planting cover crops and mulching.

When clearing land for cultivation, the beneficial effects of certain trees and plants should be considered. Some trees should be left, since they may supply food, medicine, shade or, when they shed their leaves, organic matter.


Feeding the Soil

One of the main goals in growing crops is to make the soil fertile and well structured, so a wide range of useful crops can grow and produce well. In order to grow, plants require nutrients that are present in organic matter, such as nitrogen, calcium and phosphorus, as well as minerals and trace elements.


If the natural fertility or structure of the soil is poor, it must be continuously "fed" with organic matter, such as leaves and manure, in order to improve its productivity and water-holding capacity. As organic matter decomposes, it becomes food for plants. It also improves soil structure by loosening heavy clay and binding sandy soil.


Feeding the soil with organic matter is especially important in the early years of cultivating the land. Organic matter (i.e. waste from plants and livestock) can be collected and buried in the soil, where it will decompose. The organic matter also can be used to make compost, which can be applied to the soil to enrich its fertility.


The roots of legumes contain nitrogen-fixing bacteria. Therefore, intercropping or rotating legumes with other crops helps maintain or improve the nitrogen content of the soil, and this enhances the growth of other plants.


Healthy plants yield more and are better protected from insects and disease. The application of organic matter, such as compost, animal manure, green manure and soil from anthills, improves soil structure and adds nutrients to the soil.


Long-Term Soil Management

The ideal way to protect and feed the soil is to apply organic matter or compost regularly and to keep the soil covered with plants. A multilayer cropping system in which a mixture of trees and other plants with different maturity times are grown together will protect the soil and recycle nutrients. Leguminous plants such as cowpeas, groundnuts and beans are particularly useful in providing continuous nutrients for crops.


Apply Organic Matter to Soil to Improve the Crop

Plants can contain up to 90 percent water. The water is absorbed mainly through the root system of the plant. With the water, plant nutrients are absorbed. Healthy roots need air (aeration) for development. Excess water in the soil prevents air from penetrating and damages a plant's roots. Water management is therefore extremely important in regions with good water resources as well as in those where water is scarce.


The water-holding capacity of soil varies according to soil type. Soil with a high content of organic matter has better aeration, better structure and better water-holding capacity. Heavy, sticky soils are too dense to allow air in and water out, so roots cannot breathe and plants can have growth problems. When this kind of soil dries out, it sets like cement, and water takes a long time to soak into it. On the other hand, sandy, coarse-grained soils are too loose to hold water before it drains away. In this kind of soil, without a regular external water supply, a plant's roots cannot find enough water for growth. Regular application of organic matter will improve the ability of both these kinds of soil to hold and release enough water and air. During land preparation for planting, organic materials such as animal manure or compost should be applied to the land such that they are well incorporated into the soil.


Sources
1. African Soil Information Service (AfSIS), 2014. (http://www.africasoils.net/)
2. How to Improve Soils (http://www.howtoimprovesoils.info/kinds-of-soils/clay-soils-clay-loams-loam-soils.html)
3. University of Arizona (http://ag.arizona.edu/pubs/garden/mg/soils/principal.html)
4. Wikipedia.org, "Soil pH" (http://en.wikipedia.org/wiki/Soil_pH)
5. PlanTea (http://www.plantea.com/pH.htm)
6. Wikipedia.org, "Tropical Agriculture" (http://en.wikipedia.org/wiki/Tropical_agriculture#Acidic_soils)
7. Wikipedia.org, "Alkali soils" (http://en.wikipedia.org/wiki/Alkali_soils)
8. Spectrum Analytic (http://www.spectrumanalytic.com/support/library/ff/CEC_BpH_and_percent_sat.htm)
9. FAO/IIASA/ISRIC/ISS-CAS/JRC, 2009. Harmonized World Soil Database (version 1.1). FAO, Rome, Italy and IIASA, Laxenburg, Austria (http://www.iiasa.ac.at/Research/LUC/External-World-soil-database/HWSD_Documentation.pdf)
10. Pennsylvania State University (http://pubs.cas.psu.edu/FreePubs/pdfs/uc038.pdf)
11. Clemson University (hubcap.clemson.edu/~blpprt/IL64.html)
12. Department of Primary Industries, Victoria, Australia (http://www.dpi.vic.gov.au/dpi/vro/vrosite.nsf/pages/soil_mgmt_subsoil_pdf/$FILE/BCG_subsoils_09_ch05.pdf)
13. Soil Quality for Environmental Health (http://soilquality.org/indicators/bulk_density.html)
14. Amacher, Michael C.
15. O’Neil, Katherine P.
16. Perry, Charles H. 2007. Soil vital signs: A new Soil Quality Index (SQI) for assessing forest soil health. Res. Pap. RMRS-RP-65WWW. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 12 p. (http://www.fs.fed.us/rm/pubs/rmrs_rp065.pdf)
17. Andre Bationo, Job Kihara, Bernard Vanlauwe, Boaz Waswa, Joseph Kimetu, "Soil organic carbon dynamics, functions and management in West African agro-ecosystems", Received 8 February 2005
18. accepted 18 August 2005 (http://www.zef.de/module/register/media/18ea_sdarticle.pdf)
19. eHow (http://www.ehow.com/list_7256066_loam-soil-plants.html)
20. World reference base for soil resources 2006. 2nd edition. World Soil Resources Reports No. 103. FAO, Rome, page 80 (http://www.fao.org/ag/agl/agll/wrb/doc/wrb2006final.pdf)
21. Lecture Notes on the Major Soils of the World, FAO, Rome, 2001, page 105-106 (http://www.itc.nl/~rossiter/Docs/WRB/wsrr94e.pdf).
22. CT ECO (http://www.cteco.uconn.edu/guides/Soils_Drainage.htm)
23. McDonald, A.J., Cornell University, "Soil Drainage Classification and Hydric Soil Indicators" (http://www.css.cornell.edu/courses/260/Lab%20Hydric%20Soils.pdf), last modified on August 8, 2002.
24. FAO (http://www.fao.org/nr/land/soils/harmonized-world-soil-database/soil-quality-for-crop-production/en/).
25. FAO (http://www.fao.org/nr/land/soils/harmonized-world-soil-database/soil-quality-for-crop-production/en/)
26. FAO, AGL ProSoil (http://www.fao.org/ag/AGL/agll/prosoil/calc.htm)
27. Grameen Foundation (www.grameenfoundation.org)
28. Mississippi State University (http://msucares.com/lawn/garden/vegetables/soil/index.html)
29. World reference base for soil resources 2006. 2nd edition. World Soil Resources Reports No. 103. FAO, Rome (http://www.fao.org/ag/agl/agll/wrb/doc/wrb2006final.pdf)
30. BBC (http://www.bbc.co.uk/gardening/htbg/module1/soil_types1.shtml)
31. University of Florida (http://edis.ifas.ufl.edu/tr004)
32. Which? (http://www.which.co.uk/documents/pdf/growing-on-gravel-154029.pdf)
33. eHow.com (http://www.ehow.com/how_7626870_garden-gravelly-soil.html)
34. FAO/IIASA/ISRIC/ISS-CAS/JRC, 2009. Harmonized World Soil Database (version 1.1). FAO, Rome, Italy and IIASA, Laxenburg, Austria (http://www.iiasa.ac.at/Research/LUC/External-World-soil-database/HWSD_Documentation.pdf).
35. University of Florida (http://edis.ifas.ufl.edu/ss169)
36. PROSEA: Plant Resources of South–East Asia (www.proseanet.org)
37. PROTA: Plant Resources of Tropical Africa (http://www.prota.org/)
38. EcoPort Programme, FAO (http://ecoport.org/)
39. Lecture Notes on the Major Soils of the World, FAO, Rome, 2001 (http://www.itc.nl/~rossiter/Docs/WRB/wsrr94e.pdf).
40. eHow.com (http://www.ehow.com/list_7464662_list-grow-different-soil-types.html#ixzz1YRUWbhI5)
41. Discovery Education (http://school.discoveryeducation.com/schooladventures/soil/name_soil.html)
42. Wikipedia.org, "Soil Salinity Control" (http://en.wikipedia.org/wiki/Soil_salinity_control), last modified on January 19, 2012.
43. FAO, "Management of Gypsiferous Soils" (http://www.fao.org/docrep/t0323e/t0323e00.htm#Contents)
44. Soil Quality for Environmental Health (http://soilquality.org/indicators/bulk_density.html).
45. USDA (http://soils.usda.gov/sqi/publications/files/sq_two_1.pdf).
46. Rhoades, Heather, "Adding Nitrogen As A Plant Fertilizer," Gardening Know How (http://www.gardeningknowhow.com/gardening-how-to/nitrogen-plant-fertilizer.htm)
47. Perry, Charles H. 2007. Soil vital signs: A new Soil Quality Index (SQI) for assessing forest soil health. Res. Pap. RMRS-RP-65WWW. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 12 p. (http://www.fs.fed.us/rm/pubs/rmrs_rp065.pdf).
48. Rhoades, Heather, "The Importance Of Phosphorus In Plant Growth," Gardening Know How (http://www.gardeningknowhow.com/gardening-how-to/phosphorus-plant-growth.htm)
49. Rhoades, Heather, "Plants And Potassium: Using Potassium And Potassium Deficiency In Plants," Gardening Know How (http://www.gardeningknowhow.com/gardening-how-to/plants-potassium.htm)
50. World reference base for soil resources 2006. 2nd edition. World Soil Resources Reports No. 103. FAO, Rome, page 94 (http://www.fao.org/ag/agl/agll/wrb/doc/wrb2006final.pdf)
51. Lecture Notes on the Major Soils of the World, FAO, Rome, 2001, page 201 (http://www.itc.nl/~rossiter/Docs/WRB/wsrr94e.pdf).
52. World reference base for soil resources 2006. 2nd edition. World Soil Resources Reports No. 103. FAO, Rome, page 92 (http://www.fao.org/ag/agl/agll/wrb/doc/wrb2006final.pdf).
53. Wikipedia (www.wikipedia.org)
54. World reference base for soil resources 2006. 2nd edition. World Soil Resources Reports No. 103. FAO, Rome, page 88 (http://www.fao.org/ag/agl/agll/wrb/doc/wrb2006final.pdf)
55. Lecture Notes on the Major Soils of the World, FAO, Rome, 2001, page 253 (http://www.itc.nl/~rossiter/Docs/WRB/wsrr94e.pdf)
56. FAO/AGL, 2003 (http://www.fao.org/ag/agl/agll/wrb/soilres.stm).
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