As a medium in which roots grow and as a reservoir for water and nutrients on which crops continuously draw during their life cycle, soils are natural resource and valuable economic asset requiring protection, conservation and improvement through good husbandry.
The adequate agricultural exploitation of the climatic potential and sustained maintenance of productivity largely depends on soil fertility and management of soil on an ecologically sound basis. Soil fertility is concerned with the ability of the soil to supply nutrients and water to enable crops to maximize the climatic resources of a given location. The fertility of a soil is determined by its both physical and chemical properties whose understanding is essential to the effective utilization of climate and crop resources for optimum production.
In order to assess suitability of soils for crop production, soil requirements of crops must be known. Further, these requirements must be understood within the context of limitations imposed by landform and other features which do not form a part of soil but may have a significant influence on the use that can be made of the soil.
The basic soil requirements of crop plants may be summarized under the following headings, related to internal and external soil properties:
Internal requirements:
- the soil temperature regime, as a function of the heat balance of soils as related to annual or seasonal and/or daily temperature fluctuations;
- the soil moisture regime, as a function of the water balance of soils as related to the soil's capacity to store, retain, transport and release moisture for crop growth, and/or to the soil's permeability and drainage characteristics;
- the soil aeration regime, as a function of the soil air balance as related to its capacity to supply and transport oxygen to the root zone and to remove carbon dioxide;
- the natural soil fertility regime, as related to the soil's capacity to store, retain and release plant nutrients in such kinds and proportions as required by crops during growth;
- the effective soil depth available for root development and foothold of the crop;
TABLE 6.1 Crop edaphic adaptability inventory
CROP | SLOPE (PERCENT) | DRAINAGE | ||||
High inputs | Low & Int. inputs | All inputs | ||||
Optimum | Marginal | Optimum | Marginal | Optimum | Range | |
Barley | 0–8 | 8–16 | 0–8 | 8–24 | MW-W | I-SE |
Oat | 0–8 | 8–16 | 0–8 | 8–24 | MW-W | I-SE |
Cowpea | 0–8 | 8–16 | 0–8 | 8–20 | MW-W | I-SE |
Green gram | 0–8 | 8–16 | 0–8 | 8–20 | MW-W | I-SE |
Pigeon pea | 0–8 | 8–16 | 0–8 | 8–20 | MW-W | I-SE |
Drainage classes - I = imperfectly drained;
SE = somewhat excessively drained;
E = excessively drained.
CROP | FLOODING | TEXTURE | ||||
All Inputs | High inputs | Low & Int. inputs | ||||
Optimum | Marginal | Optimum | Range | Optimum | Range | |
Barley | Fo | F1 | L-MCs | SL-MCs | L-SC | SL-KC |
Oat | Fo | F1 | L-C | SL-MCs | L-SC | SL-KC |
Cowpea | Fo | F1 | SL-SCL | LS-KC | SL-SCL | LS-KC |
Green gram | Fo | F1 | L-CL | SL-KC | L-CL | LS-KC |
Pigeon pea | Fo | F1 | SL-SCL | LS-KC | SL-SCL | LS-KC |
Flooding classes - Fo = no floods;
Texture classes - MCs = montmorillonitic clay, structured;
SiCL = silty clay loam;
CROP | DEPTH (cm) | CaCO3(%) | GYPSUM (%) | |||
All inputs | All inputs | All inputs | ||||
Optimum | Marginal | Optimum | Marginal | Optimum | Marginal | |
Barley | > 50 | 25–50 | 0–30 | 30–60 | 0–5 | 5–20 |
Oat | > 50 | 25–50 | 0–30 | 30–60 | 0–5 | 5–20 |
Cowpea | > 75 | 50–75 | 0–20 | 20–35 | 0–3 | 3–15 |
Green gram | > 75 | 50–75 | 0–25 | 20–35 | 0–3 | 3–15 |
Pigeon pea | > 100 | 50–100 | 0–25 | 20–50 | 0–3 | 3–15 |
CROP | PH | FERTILITY REQUIREMENTS | SALINITY (mmhos/cm) | ||
All inputs | All inputs | All inputs | |||
Optimum | Range | Range | Optimum | Range | |
Barley | 6.0–7.5 | 5.2–8.5 | moderate | 0–8 | 8–12 |
Oat | 6.0–7.5 | 5.2–8.2 | low/moderate | 0–5 | 5–10 |
Cowpea | 5.2–7.5 | 5.0–8.2 | low/moderate | 0–3 | 3–6 |
Green gram | 5.5–7.5 | 5.2–8.2 | moderate | 0–3 | 3–6 |
Pigeon pea | 5.2–7.5 | 5.0–8.2 | low/moderate | 0–3 | 3–6 |
CROP | ALKALINITY (ESP) | |
All inputs | ||
Optimum | Marginal | |
Barley | 0–35 | 35–50 |
Oat | 0–30 | 30–45 |
Cowpea | 0–5 | 8–12 |
Green gram | 0–5 | 8–12 |
Pigeon pea | 0–5 | 8–12 |
- soil texture at the surface and within the whole depth of soil required for normal crop development;
- the absence of soil salinity and of specific toxic substance or ions deleterious to crop growth;
- other specific properties, e.g. soil tilth as required for germination and early growth.
External requirements: in addition to the above internal soil requirements of crops, a number of external soil requirements are of importance, e.g.:
- soil slope, topography and characteristics determined by micro and macrorelief of the soil;
- occurrence of flooding as related to crop susceptibility to flooding during the growing period;
- soil accessibility and trafficability under certain management systems.
From the basic soil requirements of crops, a number of crop response related soil characteristics can be derived. One of these characteristics is, for instance, soil pH. For most crops and cultivars, optimal soil pH is known and can be quantified by a range within which it is not limiting to growth. Outside the optimal range, there is a critical range within which the crop can be grown successfully but with diminished yield. Beyond the critical range, the crop cannot be expected to yield satisfactorily unless special precautionary management measures are taken.
The same holds for other soil requirements of plants related to soil characteristics. Many soil characteristics can be defined in a range that is optimal for a given crop, a range that is critical or marginal, and a range that is unsuitable under present technology.
Table 6.1 presents for barley, oat, cowpea, green gram and pigeonpea, optimal and critical ranges of the following soil characteristics: soil slope, soil depth, soil drainage, flooding, texture and clay type, natural fertility (including cation exchange capacity, percent base saturation and organic matter), salinity, pH, free calcium carbonate content and gypsum content.
Symbol | Name |
A | Acrisols |
Ac | Chromic Acrisols |
Ag | Gleyic Acrisols |
Ah | Humic Acrisols |
Aic | Ferralo-chromic Acrisols |
Aif | Ferralo-ferric Acrisols |
Aio | Ferralo-orthic Acrisols |
Ao | Orthic Acrisols |
Ap | Plinthic Acrisols |
Ath | Ando-humic Acrisols |
B | Cambisols |
Bc | Chromic Cambisols |
Bd | Dystric Cambisols |
Be | Eutric Cambisols |
Bf | Ferralic Cambisols |
Bg | Gleyic Cambisols |
Bh | Humic Cambisols |
Bk | Calcic Cambisols |
Bnc | Nito-chromic Cambisols |
Btc | Ando-chromic Cambisols |
Bte | Ando-eutric Cambisols |
Bv | Vertic Cambisols |
Ch | Haplic Chernozems |
Ck | Calcic Chernozems |
Ec | Cambic Renzinas |
Eo | Orthic Renzinas |
F | Ferralsols |
Fa | Acric Ferralsols |
Fh | Humic Acrisols |
Fnh | Nito-humic Ferralsols |
Fnr | Nito-rodic Ferralsols |
Fo | Orthic Ferralsols |
Fr | Rodic Ferralsols |
Fx | Xanthic Ferralsols |
G | Gleysols |
Gc | Calcaric Gleysols |
Gd | Dystric Gleysols |
Go | Eutric Gleysols |
Gh | Humic Gleysols |
Gm | Mollic Gleysols |
Gv | Vertic Gleysols |
Hg | Gleyic Phaeozems |
Hh | Haplic Phaeozems |
Hnl | Nito-luvic Phaeozems |
Hol | Ortho-luvic Phaeozems |
Hrl | Chromic-luvic Phaeozems |
Hth | Ando-haplic Phaeozems |
Htl | Ando-luvic Phaeozems |
Hvl | Verto-luvic Phaeozems |
I | Lithosols |
Ir | Ironstone soils |
J | Fluvisols |
Jc | Calcaric Fluvisols |
Je | Eutric Fluvisols |
Jt | Thionic Fluvisols |
Kh | Haplic Kastanozems |
L | Luvisols |
LA | Albic Luvisols |
Lc | Chromic Luvisols |
Lf | Ferric Luvisols |
Lg | Gleyic Luvisols |
Lic | Ferralo-chromic Luvisols |
Lif | Ferralo-ferric Luvisols |
Lio | Ferralo-orthic Luvisols |
Lk | Calcic Luvisols |
Lnc | Nito-chromic Luvisols |
Lnf | Nito-ferric Luvisols |
Lo | Orthic Luvisols |
Lv | Vertic Luvisols |
Mo | Orthic Greyzems |
Mvo | Verto-orthic Greyzems |
Nd | Dystric Nitisols |
Ne | Eutric Nitisols |
Nh | Humic Nitisols |
Nm | Mollic Nitisols |
Nth | Ando-humic Nitisols |
Nve | Verto-eutric Nitisols |
Nvm | Verto-mollic Nitisols |
Od | Dystric Histosols |
a | Arenosols |
Oa | Albic Arenosols |
Qc | Cambic Arenosols |
Qf | Ferralic Arenosols |
Qkc | Calcaro-cambic Arenosols |
Ql | Luvic Arenosols |
R | Regosols |
Rc | Calcaric Regosols |
Rd | Dystric Regosols |
Re | Eutric Regosols |
Rtc | Ando-calcaric Regosols |
S | Solonetz |
Sg | Gleyic Solonetz |
Slo | Luvo-orthic Solonetz |
Sm | Mollic Solonetz |
So | Orthic Solonetz |
Th | Humic Andosols |
Tm | Mollic Andosols |
Tv | Vitric Andosols |
U | Rankers |
V | Vertisols |
Vc | Chromic Vertisols |
Vp | Pellic Vertisols |
W | Planosols |
Wd | Dystric Planosols |
We | Eutric Planosols |
Wh | Humic Planosols |
Ws | Solodic Planosols |
Wve | Verto-eutric Planosols |
X | Xerosols/Yermosols |
Xh | Haplic Xerosols/Yermosols |
Xk | Calcic Xerosols/Yermosols |
Xy | Gypsic Xerosols/Yermosols |
Z | Solonchaks |
Zg | Gleyic Solonchaks |
Zo | Orthic Solonchaks |
Zt | Takyric Solonchaks |
Many of the soil characteristics listed above are at least partly intrinsically related to the soil. This relationship has guided the definition of optimal and marginal ranges of the various soil characteristics and so simplified the subsequent matching of the different soil units with the inventoried soil requirements of crops.
The soil resources of Kenya (Technical Annex 1) have been inventoried in terms of associations of soil units, and the corresponding characterization of soil textures, phases, stoniness and slopes.
Soil units have been defined in terms of measurable and observable properties of the soil itself, and specific clusters of such properties are combined into ‘diagnostic horizons’ and soil units. The soil units inventoried in the Kenya soil resources inventory (Exploratory Soil Map of Kenya) are listed in Table 6.2.
Soil texture may vary within the range of textures defined for a particular soil unit. In the legend of the Exploratory Soil Map, textural classes for the individual soil units by soil mapping unit are presented. The three major textural divisions (coarse, medium and fine) are subdivided into 17 classes (Table 6.3) Soil phases indicate land characteristics which are not considered in the definition of the soil units but are significant to the use and management of land. Soil phases recognized on the Exploratory Soil Map of Kenya can be grouped into phases indicating a mechanical hindrance or limitation (rocky, bouldery, boulder-mantle, stony, stone-mantle, gravel-mantle), phases indicating an effective soil depth limitation (lithic, paralithic, petro-calcic, piso-calcic, petro-ferric, piso-ferric), and phases indicating a physico-chemical limitation (saline, sodic and saline-sodic). Soil phases occur either individually or in combinations of up to three. They are described in Technical Annex 1, and are listed in Table 6.4.
Texture Symbol | Texture class |
Coarse: | |
S | Sand |
LCS | Loamy coarse sand |
FS | Fine sand |
LFS | Loamy fine sand |
LS | Loamy sand LS |
Medium: | |
FSL | Fine sandy loam |
SL | Sandy loam |
L | Loam |
SCL | Sandy clay loam |
SL | Silt loam |
CL | Clay loam |
SIL | Silty clay loam |
SI | Silt |
Fine: | |
SC | Sandy clay |
SIC | Silty clay |
PC | Peaty clay |
C | Clay |
The presence of coarse material (stoniness) in the soil profile has been inventoried seperately from soil textures. Six types of coarse material or stoniness have been inventoried: Gravelly (G), Very Gravelly (VG), Stony (S), Bouldery (B), Stony/Bouldery (SB) and Bouldery/Stony (BS).
Six basic slope classes, in 12 combinations, have been employed in the Exploratory Soil Map of Kenya. The six basic slope classes are: A: 0–2%; B: 2–5%; C: 5–8%; D: 8–16%; E: 16–30% and F: > 30%. The 12 combination slope classes are: A: 0–2%; AB: 0–5%; B: 25%; BC: 2–8%; C: 5–8%; BCD: 2–16%; CD: 5–16%; D: 8–16%; DE: 8–30%; E: 16–30%; EF: 16->30%; F: >30%.
To each of these 12 slope classes, associated slope classes have been assigned. These associated slope classes, covering upto 10% of the land area of the 12 slope classes, are used for evaluation purposes only. They are not included explicitly in the soil resources inventory. The 12 inventoried combination slope classes and the associated slope classes are presented in Table 6.5. For the same purposes of evaluation, assumed mean slopes have been assigned to each of the quartiles of the land area of each of the 12 slope classes (Table 6.6).
Symbol | Name | Symbol | Name | Symbol | Name |
Single.: | Combination of two: | Combination of three: | |||
R | Rocky | R/B | Rocky and bouldery | R/B/AO | Rocky and bouldery and saline-sodic |
B | Bouldery | R/S | Rocky and Many | ROTS | Rocky and lithic and stony |
BM | Boulder-mentle | B/S | Bouldery and stony | B/S/A | Bouldery and stony and saline |
S | Stony | BM/AO | Boulder-mantle and saline-saline-sodic | BM/S/AO | Bouldery and atony and saline-sodic |
SM | Stone mantle | S/R | Stoney and rocky | P/R/B | Lithic and rocky and bouldery |
G | Gravelly | S/B | Stony and bouldery | P/R/S | Lithic and rocky and atony |
GM | Gravel-mantle | S/K | Stony and pertrocalcic | P/B/S | Lithic and bouldery and atony |
P | Lithic | S/AO | Stony and saline-sodic | P/B/A | Lithic and bouldery and saline |
PP | Paralithic | SM/O | Stone mantle and sodic | P/BM/AO | Lithic and bouldery-mantle and saline-sodic |
K | Petrocalcic | SM/AO | Stone mantle and saline-sodic | P/S/R | Lithic and atony and rocky |
KK | Petrocalcic | P/R | Lithic and rocky | P/S/A | Lithic and atony and saline |
C | Pisocalcic | P/B | lithic and bouldery | P/S/AO | Lithic and atony and saline-sodic |
CC | Pisocalcic | P/BM | Lithic and boulder-mantla | P/SM/AO | Lithic and stone-mantle and saline-sodic |
M | Petroferric | P/S | Lithic and stony | P/GM/S | Lithic and gravel-mantle and saline |
MM | Pisoferric | P/O | Lithic and sodic | ||
A | Saline | P/AO | Lithic and saline-sodic | ||
O | Sodic | PP/R | Paralithic and rocky | ||
AO | saline-sodic | PP/S | Paralithic and atony | ||
F | Fragipan | K/S | Petrocalcic and stony | ||
K/A | Petrocalcic and saline-sodic | ||||
KK/A | Petrocalcic and saline | ||||
KK/O | Petrocalcic and sodic | ||||
M/R | Pisoferric and rocky | ||||
M/M | Pisoferric and pisoferric | ||||
A/F | Pisoferric and fragipan | ||||
O/F | Sodic and fragipan |
From the basic soil requirements of crops, a number of responses related soil characteristics can be derived. A correlation between soil requirements listed above and soil characteristics that can be used as soil factors to rate crop performance is given in Table 6.7.
As explained earlier, the soil units (Table 6.2) have been defined in terms of measurable and observable properties of the soil itself, and specific clusters of such properties are combined into ‘diagnostic properties’, which are used in the definition of the soil units.
TABLE 6.5
Associated slope classes
Slope class | Associated slope classes | ||||||
symbol | % | ||||||
A | 0 – 2 | 100% | A | ||||
AB | 0 – 5 | 100% | AB | ||||
B | 2 – 5 | 100% | B | ||||
BC | 2 – 8 | 90% | BC | 5% | A | 5% | D |
C | 5 – 8 | 90% | C | 5% | AB | 5% | D |
BCD | 2 – 16 | 90% | BCD | 5% | A | 5% | E |
CD | 5 – 16 | 90% | CD | 5% | AB | 5% | E |
D | 8 – 16 | 90% | D | 5% | BC | 5% | E |
DE | 8 – 30 | 90% | DE | 5% | BC | 5% | F |
E | 16 – 30 | 90% | E | 5% | BCD | 5% | F |
EF | 16 – 56 | 95% | EF | 5% | BCD | ||
F | 30 – 56 | 95% | F | 5% | DE |
The diagnostic horizons have been used as defined in the FAO/Unesco Soil Map of the World Legend. Diagnostic properties however have been narrowed down in case of ferric properties and widened in case of vertic properties. In Table 6.8 for each soil unit diagnostic horizons and properties of the soil units are summarized. For the ease of interpretation of Table 6.8 these characteristics are summarized below.
TABLE 6.6
Quartiles of slope classes
Slope | class | Gentlest | Lower | Upper | Steepest |
symbol | % | Q1 | Q2 | Q3 | Q4 |
A | 0 – 2 | 0 | 1 | 1 | 2 |
AB | 0 – 5 | 0 | 2 | 4 | 5 |
B | 2 – 5 | 2 | 3 | 4 | 5 |
BC | 2 – 8 | 2 | 4 | 6 | 8 |
C | 5 – 8 | 5 | 6 | 7 | 8 |
BCD | 2 – 16 | 2 | 6 | 11 | 16 |
CD | 5 – 16 | 5 | 9 | 12 | 16 |
D | 8 – 16 | 8 | 11 | 13 | 16 |
DE | 8 – 30 | 8 | 16 | 22 | 30 |
E | 16 – 30 | 16 | 21 | 25 | 30 |
EF | 16 – 56 | 16 | 30 | 42 | 56 |
F | 30 – 56 | 30 | 39 | 47 | 56 |
TABLE 6.7
Relation between basic soil requirements for crops and soil characteristics
Basic soil requirements | Soil characteristics (soil factors) |
Moisture availaibility1 | - Effective soil depth |
- Available soil moisture holding capacity | |
- Drainage | |
Nutrient availability | - Nutrient availability |
- Soil reaction | |
Oxygen availability2 | - Soil permeability |
- Drainage | |
Foothold for roots | - Effective soil depth |
Salinity | - Soil salinity |
Toxicity | - Soil reaction3 |
Accessibility and trafficability (workability) | - Topsoil consistency and bearing capacity |
Soil tilth for crop establishment | - Topsoil consistency and bearing capacity |
1 Moisture availability is influenced by climatic factors
2 Oxygen availability is influenced by inundation and flooding characteristics
3 Chemical properties of soil parent material may also be involved in some cases.
Histic H horizon: | Surface layer of organic material more than 20 cm thick. |
MOLLIC A horizon: | Surface horizon with dark colour, medium to high humus content, high base saturation. |
Umbric A horizon: | Surface horizon with dark colour, medium to high humus content, low base saturation. |
Ochric A horizon: | Surface horizon with light colour, low humus content. |
Argillic B horizon: | Subsoil horizon with accumulation of illuvial clay. |
Natric B horizon: | Subsoil horizon with accumulation of illuvial clay and high exchangeable sodium. |
Cambic B horizon: | Subsoil horizon with a structure and/or colour different from overlying and underlying horizons. |
Spodic B horizon: | Subsoil horizon with accumulation of iron and/or humus. |
Oxic B horizon: | Subsoil with residual accumulation of sesquioxides and low CEC. |
Calcic horizon: | Horizon of accumulation of calcium carbonate. |
Gypsic horizon: | Horizon of accumulation of calcium sulphate. |
Sulphuric horizon: | Horizon with strong acidity and prominent mottling. |
Albic E horizon: | Eluvial horizon from which clay and free iron oxide have been removed, light colour. |
Calcareous material: | Calcium carbonate present at least between 20 and SO cm from the surface. CEC high or very high: Exchange complex dominated by allophane or montmorillonite. |
CEC low: | Exchange complex dominated by kaolinite (CEC less than 24 meq/100 g clay). |
CEC very -low: | Less than l.5 meq/100 g clay. |
Cracking clays: | Formation of deep and wide cracks upon drying. |
Plinthite: | Mottled subsoil layer which irreversibly hardens upon exposure to repeated wetting and drying. |
High salinity: | Electrical conductivity (EC) higher than 15 mmhos/cm. |
Moderate salinity: | Electrical conductivity (EC) between 4 and 15 mmhos/cm. |
High alkalinity: | Saturation with exchangeable sodium of more than 15 percent. |
Moderate alkalinity: | Saturation with exchangeable sodium of 6 to 15 percent. |
Indurated subsoil: | Subsoil layer with firm or hard consistence, but can still be penetrated by spade or auger. |
Cemented hardpan: | Extremely hard continuous subsoil layer which cannot be penetrated by spade or auger. |
Coarse texture: | Less than 18 percent clay and more than 65 percent sand. |
Heavy texture: | More than 35 percent clay. |
Abrupt textural change: | Considerable increase in clay content within a very short vertical distance. |
Tonguing: | Deep and irregular penetration of an albic E horizon into an argillic B horizon |
The agro-edaphic suitability classification is input-specific and based on:
matching the soil requirements of crops with the soil conditions of the soil units described in the soil inventory (soil unit evaluation), and
modification of the soil unit evaluation by limitation imposed by, texture, stoniness, phase and slope conditions.
6.3.1 Soil unit evaluation
The soil unit evaluation is expressed in terms of ratings based on how far the soil conditions of a soil unit meet crop requirements under three specified levels of inputs. The appraisal is effected in five basic classes for each crop and level of inputs, i.e. very suitable (S1), suitable (S2), moderately suitable (S3), marginally suitable (S4), and not suitable (N).
A rating of S1 indicates that the soil conditions for crop production are optimal and that suppression of potential yields (if any) are assumed to be slight or nil. The rating of S2 indicates that there are slight to moderate limitation which would suppress potential yields by some 25 percent. The rating of S3 indicates sub-optimal soil conditions with moderate to severe limitations which would suppress potential yields by some SO percent. The rating of S4 indicates sub-optimal soil conditions with severe limitations which would suppress potential yields by some 75 percent. The rating of N indicates that crop production is not possible. The ratings are presented in Table 6.9 for high, intermediate and low level inputs circumstances.
6.3.2 Texture evaluation
All ratings of soils with coarse texture (sand, loamy coarse sand, fine sand, loamy fine sand and loamy sand) for the five crops are classified one class lower for 50% and two classes lower for the remaining 50% of its extents, except for Arenosols (Q), Albic Arenosols (Qa), Cambic Arenosols (Qc), Ferralic Arenosols (Qf), Calcaro-cambic Arenosols (Qkc), Luvic Arenosols (Ql) and Vitric Andosols (Tv), which should remain unchanged since coarse texture limitations have already been applied in the soil unit ratings. All ratings of soils with medium and fine textures remain unchanged since limitations imposed by these textures have been included in the soil unit ratings.
6.3.3 Stoniness evaluation
The limitations imposed by presence of coarse material (stoniness) in the soil profile have been rated (using the five basic classes described in 6.3.1) by crop and inputs level. The ratings are presented in Table 6.10.
6.3.4 Soil phase evaluation
The limitations imposed by presence of soil phases which occur individually or in combinations of up to three phases have been rated (using the five basic classes described in 6.3.1) by crop and inputs level. The ratings are presented in Table 6.11.
TABLE 6.8
Diagnostic horizons and properties of soil units
A | Ac | Ag | Ah | Aic | Aif | Aio | Ao | Ap | Ath | B | Bc | Bd | Be | Bf | Bg | Bh | Bk | Bnc | Btc | Bte | Bv | C | Ch | Ck | |
Histic H horizon | |||||||||||||||||||||||||
Hollic A horizon | X | X | X | ||||||||||||||||||||||
Unbric A horizon | (X | X | X | (X | X | ||||||||||||||||||||
Ochric A horizon | X | X | (X | X | X | X | X | X | X | X | X | X | X | (X | X | X | X | X | X | ||||||
Arqillic B horizon | X | X | X | X | X | X | X | X | X | X | |||||||||||||||
Natric B horizon | |||||||||||||||||||||||||
Cubic B horizon | X | X | X | X | X | X | X | X | X | X | X | X | X | ||||||||||||
Spodic B horizon | |||||||||||||||||||||||||
Oxic B horizon | |||||||||||||||||||||||||
Calcic horizon | X | X | |||||||||||||||||||||||
Sypsic horizon | |||||||||||||||||||||||||
Sulferic horizon | |||||||||||||||||||||||||
Albic E horizon (tat.) | |||||||||||||||||||||||||
Calcareous material | X | X | X | ||||||||||||||||||||||
CaCO3> 5% (topsoil) | |||||||||||||||||||||||||
CEC high/very high | X | ||||||||||||||||||||||||
CEC low (< 24 meq) | X | X | X | ||||||||||||||||||||||
CEC very low (<1.5 meq) | X | ||||||||||||||||||||||||
Base sat. > 50%, (ph>5.5) | X | X | X | X | X | X | X | X | X | X | |||||||||||||||
Base sat. < 50%. (pH<5.5) | X | X | X | X | X | X | X | X | X | X | X | X | |||||||||||||
Cracking clay | X | ||||||||||||||||||||||||
teeth (25 cm | |||||||||||||||||||||||||
Depth 25–50 cm | |||||||||||||||||||||||||
Drainage very poor/poor | X | ||||||||||||||||||||||||
Drainage inp./moderate | X | X | |||||||||||||||||||||||
Drainage excessive | |||||||||||||||||||||||||
Plinthite | X | ||||||||||||||||||||||||
Salinity high | |||||||||||||||||||||||||
Salinity moderate | |||||||||||||||||||||||||
Alkalinity high | |||||||||||||||||||||||||
Alkalinity Moderate | |||||||||||||||||||||||||
Indurated subsoil | |||||||||||||||||||||||||
Cemented hardpan | |||||||||||||||||||||||||
Iron concretions | X | X | |||||||||||||||||||||||
Texture coarse | |||||||||||||||||||||||||
Texture heavy | X | X | X | X | |||||||||||||||||||||
Abrubt textural change | |||||||||||||||||||||||||
Tonguing | |||||||||||||||||||||||||
Reddish colour | X | X | X | X | X | ||||||||||||||||||||
Yellowish colour | |||||||||||||||||||||||||
Hat. fertility high | X | X | X | X | X | X | X | X | X | ||||||||||||||||
Nat. fertility moderate | X | X | X | X | X | X | X | X | X | X | X | X | |||||||||||||
Hat. fertility low | X | X | X | X | |||||||||||||||||||||
A | Ac | Ag | Ah | Ac | Aif | Aio | Ao | Ap | Ath | B | Bc | Bd | Be | Bf | Bg | Bh | Bk | Bnc | Btc | Bte | Bv | C | Ch | Ck |
(indicates autually exclusive horizons)
E | Ec | Eo | F | Fa | Fh | Fnh | Fnr | Fo | Fr | Fx | G | Gc | Gd | Ge | Gh | Gn | Gv | H | Hg | Hh | Hnl | Hol | Hrl | Hth | |
Histic H horizon | (x | (x | |||||||||||||||||||||||
Mollic A horizon | X | X | X | (X | X | X | X | X | X | X | X | ||||||||||||||
Umbric A horizon | X | X | (X | ||||||||||||||||||||||
Ochric A horizon | X | X | X | X | X | X | X | X | X | X | X | ||||||||||||||
Argillic B horizon | X | ||||||||||||||||||||||||
Nitric B horizon | |||||||||||||||||||||||||
Cubic B horizon | X | X | X | X | X | X | X | X | X | X | |||||||||||||||
Spodic B horizon | |||||||||||||||||||||||||
Oxic B horizon | X | X | X | X | X | X | X | X | |||||||||||||||||
Calcic horizon | X | ||||||||||||||||||||||||
Gypsic horizon | |||||||||||||||||||||||||
Sulferic horizon | |||||||||||||||||||||||||
Albic E horizon (Mat.) | |||||||||||||||||||||||||
Calcareous material | X | X | X | X | |||||||||||||||||||||
CaCO3 > 5% (topsoil) | X | ||||||||||||||||||||||||
CEC high/very high | |||||||||||||||||||||||||
CEC lot (< 24 meq) | X | X | X | X | X | X | X | ||||||||||||||||||
CEC very lot (< 1.5 meq) | X | ||||||||||||||||||||||||
Base sat. > 50%, (pH > 5.5) | X | X | X | X | |||||||||||||||||||||
Base sat. (502, (pH > 5.5) | X | X | X | X | X | X | |||||||||||||||||||
Cracking clay | X | ||||||||||||||||||||||||
Depth < 25 cm | |||||||||||||||||||||||||
Depth 25–50 cm | X | X | X | ||||||||||||||||||||||
Drainage very poor/poor | X | X | X | X | X | X | X | X | |||||||||||||||||
Drainage imp./moderate | |||||||||||||||||||||||||
Drainage excessive | |||||||||||||||||||||||||
Plinthite | |||||||||||||||||||||||||
Salinity high | |||||||||||||||||||||||||
Salinity moderate | |||||||||||||||||||||||||
Alkalinity high | |||||||||||||||||||||||||
Alkalinity nitrate | |||||||||||||||||||||||||
Indurated subsoil | |||||||||||||||||||||||||
Cemented hardpan | |||||||||||||||||||||||||
Iron concretions | |||||||||||||||||||||||||
Texture coarse | X | ||||||||||||||||||||||||
Texture heavy | X | X | |||||||||||||||||||||||
Abrubt textural change | |||||||||||||||||||||||||
Tonguing | |||||||||||||||||||||||||
Reddish colour | X | X | |||||||||||||||||||||||
Yellowish colour | X | ||||||||||||||||||||||||
Hat. fertility high | X | X | X | X | X | X | X | X | X | X | X | ||||||||||||||
Nat. fertility moderate | X | X | X | X | X | ||||||||||||||||||||
Hat. fertility low | X | X | X | X | |||||||||||||||||||||
E | Ec | Eo | F | Fa | Fh | Fnh | Fnr | Fo | Fr | Fx | G | Gc | Gd | Ge | Gh | Gn | Gv | H | Hg | Hh | Hnl | Hol | Hrl | Hth |
(indicates autually exclusive horizons)
Htl | Hvl | I | Ir | J | Jc | Je | Jt | K | Kh | L | La | Lc | Lf | Lg | Lic | Lif | Lio | Lk | Lnc | Lnf | Lo | Lv | M | Mo | |
Histic B horizon | |||||||||||||||||||||||||
Hollic A horizon | X | X | X | X | X | X | |||||||||||||||||||
Umbric A horizon | (X | ||||||||||||||||||||||||
Ochric A horizon | X | X | X | (X | X | X | X | X | X | X | X | X | X | X | X | X | X | ||||||||
Argillic B horizon | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | ||||||||
Matric B horizon | |||||||||||||||||||||||||
Cubic & horizon | X | X | |||||||||||||||||||||||
Spodic i horizon | |||||||||||||||||||||||||
Oxic B horizon | |||||||||||||||||||||||||
Calcic horizon | X | X | |||||||||||||||||||||||
Gypsic horizon | |||||||||||||||||||||||||
Sulferic horizon | X | ||||||||||||||||||||||||
Albic E horizon feat.) | X | ||||||||||||||||||||||||
Calcareous material | X | X | |||||||||||||||||||||||
CaCO3 < 5% (topsoil) | |||||||||||||||||||||||||
CEC high/very high | |||||||||||||||||||||||||
CEC low (< 24 meq) | X | X | |||||||||||||||||||||||
CEC very low (< 1.5 meq) | X | X | X | ||||||||||||||||||||||
Base sat. >50%, (pH > 5.5) | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | |||||||
Base sit. < 50%, (pH < 5.5) | |||||||||||||||||||||||||
Cracking clay | X | X | |||||||||||||||||||||||
Depth (25 cm | X | ||||||||||||||||||||||||
Depth 25–50 cm | X | ||||||||||||||||||||||||
Drainage very poor/poor | X | ||||||||||||||||||||||||
Drainage imp./moderate | |||||||||||||||||||||||||
Drainage excessive | |||||||||||||||||||||||||
Plinthite | |||||||||||||||||||||||||
Salinity high | |||||||||||||||||||||||||
Salinity moderate | |||||||||||||||||||||||||
Alkalinity high | |||||||||||||||||||||||||
Alkalinity moderate | |||||||||||||||||||||||||
Indurated subsoil | |||||||||||||||||||||||||
Cemented hardpan | |||||||||||||||||||||||||
Iron concretions | X | X | X | X | |||||||||||||||||||||
Texture coarse | |||||||||||||||||||||||||
Texture heavy | X | ||||||||||||||||||||||||
Abrubt textural change | |||||||||||||||||||||||||
Tonguing | |||||||||||||||||||||||||
Reddish colour | X | X | X | ||||||||||||||||||||||
Yellowish colour | |||||||||||||||||||||||||
Hat. fertility high | X | X | X | X | X | X | X | X | X | X | X | ||||||||||||||
Nat, fertility tolerate | X | X | X | X | X | X | X | ||||||||||||||||||
Hat. fertility low | X | X | X | X | |||||||||||||||||||||
Htl | Hvi | I | Ir | J | K | Je | Jt | K | Kh | L | La | Lc | Lf | Lg | Lic | Lif | Lio | Lk | Lnc | Lnf | Lo | Lv | M | Mo |
(indicates mutually exclusive horizons)
Mvo | N | Nd | Ne | Nh | Nm | Nth | Nve | Nvm | O | Od | Q | Qa | Qc | Qf | Qk | Q1 | R | Rc | Rd | Re | Rtc | S | Sg | Slo | |
Histic H horizon | X | X | |||||||||||||||||||||||
Hollic A horizon | X | X | X | ||||||||||||||||||||||
Umbric A horizon | X | X | |||||||||||||||||||||||
Ochric A horizon | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | X | |||||||||
Argillic B horizon | X | X | X | X | X | X | X | X | X | X | |||||||||||||||
Hatric B horizon | X | X | X | ||||||||||||||||||||||
Cubic B horizon | X | X | |||||||||||||||||||||||
Spodic B horizon | |||||||||||||||||||||||||
Oxic B horizon | |||||||||||||||||||||||||
Calcic horizon | X | ||||||||||||||||||||||||
Gypsic horizon | |||||||||||||||||||||||||
Sulferic horizon | |||||||||||||||||||||||||
Albic E horizon (tat.) | |||||||||||||||||||||||||
Calcareous material | X | X | X | ||||||||||||||||||||||
CaCO3, > 5% (topsoil) | |||||||||||||||||||||||||
CEC high/very high | |||||||||||||||||||||||||
CEC low (< 24 meq) | X | ||||||||||||||||||||||||
CEC very low (< 1.5 meq) | |||||||||||||||||||||||||
Base sat. > 50% (pH > 5.5) | X | X | X | X | X | X | X | X | X | X | |||||||||||||||
Base sat. > 50%. (pH > 5.5) | X | X | X | X | X | ||||||||||||||||||||
Cracking clay | X | X | X | ||||||||||||||||||||||
Depth (25 a | |||||||||||||||||||||||||
Depth 25–50 cm | |||||||||||||||||||||||||
Drainage very poor/poor | X | ||||||||||||||||||||||||
Drainage imp./moderate | |||||||||||||||||||||||||
Drainage excessive | X | X | X | X | X | X | |||||||||||||||||||
Plinthite | |||||||||||||||||||||||||
Salinity high | |||||||||||||||||||||||||
Salinity moderate | |||||||||||||||||||||||||
Alkalinity high . | X | X | |||||||||||||||||||||||
Alkalinity Moderate | |||||||||||||||||||||||||
Indurated subsoil | |||||||||||||||||||||||||
Cemented hardpan | |||||||||||||||||||||||||
Iron concretions | X | ||||||||||||||||||||||||
Texture coarse | X | X | X | X | X | X | |||||||||||||||||||
Texture heavy | X | X | X | ||||||||||||||||||||||
Abrubt textural change | |||||||||||||||||||||||||
Tonguing | X | ||||||||||||||||||||||||
Reddish colour | |||||||||||||||||||||||||
Yellowish colour | |||||||||||||||||||||||||
Hat. fertility high | X | X | X | X | X | X | X | X | X | X | |||||||||||||||
Hat. fertility moderate | X | X | X | X | X | ||||||||||||||||||||
Hat. fertility low | X | X | X | X | X | X | X | ||||||||||||||||||
Mvo | N | Nd | Ne | Nh | Nm | Nth | Nve | Nvm | O | Od | Q | Qa | Qc | Qf | Qk | Q1 | R | Rc | Rd | Re | Rtc | S | Sg | Slo |