AGRO-ECOLOGICAL LAND RESOURCES ASSESSMENT FOR AGRICULTURAL DEVELOPMENT PLANNING - A CASE STUDY OF KENYA-TECHNICAL ANNEX 2
| World Soil Resources Reports | 71/2 |
| AGRO-ECOLOGICAL LAND RESOURCES ASSESSMENT FOR AGRICULTURAL DEVELOPMENT PLANNING - A CASE STUDY OF KENYA-TECHNICAL ANNEX 2 |
RESOURCES DATA BASE AND LAND PRODUCTIVITY
Soil Erosion and Productivity
A.H. Kassam, H.T. van Velthuizen, AJ.B. Mitchell,
G.W. Fischer and M.M. Shah
Any part of this land resources data base may be modified in the light of new knowledge and/or new objectives. The data base has been specially compiled for district and national planning, and is expected to be expanded and refined with use.
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Land and Water Development Division
Food and Agriculture Organization of the United Nations
and
International Institute for Applied Systems Analysis
Rome, 1992
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4.3 Slope Length and Gradient (LS)
5 SOIL EROSION AND LOSS OF PRODUCTIVITY
5.1 Effect of Topsoil Loss on Productivity
5.2 Effect of Soil Depth Reduction on Productivity
5.3 Assessment of Tolerable Soil Loss on a Combined 37 Basis of Topsoil Loss and Soil Depth Reduction
6.1 Estimation of Conservation Need
6.2 Costs of Conservation Measures
Figures
2.1 Schematic presentation of the soil erosion and productivity model
3.1 Make-up of land resources data base
4.1 Generalized map of the rainfall erosivity factor (R)
4.2 Generalized map of the soil erodibility factor (K)
4.3 Generalized map of the slope factor (LS)
4.4 Generalized map of potential erosion hazard
Tables
4.1 Attributes of land utilization types (single crops)
4.2 Relationships between length of growing period (LGP), mean annual rainfall (MAR) and rainfall erosivity (R)
4.3 Soil erodibility classification of soil units by soil texture
4.5 Quartiles of slope classes
4.6 Seasonal grass cover in relation to grazing by length of growing period (LGP)
4.7 Cover factor (C*) for pasture
4.8 Number of years required to reach full pasture cover by level of inputs circumstances
4.9 Cover factor (C*) due to tree and shrub canopies of different heights (soil loss as proportion to loss from bare ground)
4.10 Cover factor (C*) for undisturbed humid forest with litter layer at least 50 mm thick
4.11 Crop growth stages as percentage of the total growth cycle, for annual crops
4.12 Maximum leaf area index (LAI) of individual crops by crop growth cycle
4.13 K values for leaf canopies of individual crops
4.14 Amount of crop residues after harvest, in relation to maximum leaf area index of the crop
4.15 Cover factor (C*) for crops
4.16 Possible maximum cover density of perennial crops, and number of years to reach it
4.17 Soil loss ratios to bare fallow for flat cultivation in relation to previous crop: Subfactor Ml
4.18 Amount of crop residues remaining at the end of the dry period in relation to thermal regime, length of growing period and level of inputs
4.19 Soil protection factors for cultivation techniques other than flat cultivation: Subfactor M2
4.20 Effect of previous grass or bush fallow, from farmyard manure, and surface mulches on soil loss ratios from cultivated land: Subfactor M3
4.21 Reduction of slope-length factor due to terracing, in relation to length of unprotected slopes
4.22 P subfactor for deposition on narrow-base terraces in in relation to terrace interval and channel gradient
4.23 Protection subfactor (Ps) for slope gradient reduction by converse terraces (based on an optimum vertical interval of 1.5 m)
4.24 Protection subfactor (PI) for slope length reduction by converse terraces
4.25 Protection subfactor due to establishment of grass on terrace banks
4.26 Spacing of trash-lines related to availability of dry crop residues
4.27 Possible intervals between stone terraces related to stone cover
5.1 Slope-cultivation association screen
5.2 Regeneration capacity of topsoil (mm/year) by length of growing period (LGP) and thermal zone
5.3 Ranking of soils (Kenya Soil Survey) according to productivity loss per unit of topsoil
5.4 Relationships between topsoil loss and yield loss
5.5 The proportion of land downgraded from given depth classes to shallower depth classes or to bedrock as a result of soil erosion at different rates over a 100 year period
5.6 Tolerable rates of topsoil loss (t ha-1 year-1) to give not more than 10% loss of land from a given depth class and not more than 50% crop yield reduction at low input level over a 100-year period
6.1 Economic aspects of soil conservation measures