Soil Degradation Summary

Universal Soil Loss Equation (USLE)

E = R. K. L. S. C. P.


E = Soil lost each year

R = Rainfall erosivity index

K = Soil erodibility index

L = Length or slope

S = stripness of slopes

C = Crop management factors

P = Conservation practice factor

Soil Conservation

Consideration Strategies:

  • Protection from impact of raindrop
  • Prevention of moving water into narrow paths down the slope
  • Slowing the movement of water along the slope
  • Encourage water infiltration
  • Reduction in wind velocity

Methods of Soil Conservation

  1. Biological Methods
  2. Agronomic practices in areas of normal farming where vegetation is used for the protection of soil.
  3. Dry farming in areas of low rainfall
  4. Agrostological methods in areas suitable to successful growth of grass (binders)
  5. Mechanical Methods
  • Supplement biological increase in the time of concentration of water and reduction of water velocity
  1. Biological Methods
  2. Agronomic Practices
  1. Contour Farming
  • Farming operations are performed across the slopes
  • Increases resistance to overland flow and encourages water infiltration.
  1. Mulching – covering soil with crop residues
  2. Strip cropping – grow alternate strips of different crops

(a) Contour strip cropping

(b) Field strip

(c) Wind strip cropping wind breaks

  1. Dry farming to be followed in areas of scant rainfall, aims to conserve soil moisture
  2. Agrostological Methods
  1. Ley farming = growing grass in rotation with agricultural crops
  2. Retiring land to grasses
  1. Mechanical Methods


  • increasing absorption and reducing runoff by increasing the time of concentration
  • Dividing the slope into several short ones
  • Protection against runoff damage
  1. Basin listing = the slope is converted into a series of smaller interrupted basins
  2. Sub soiling = breaking of hard impenetrable sub soil.
  3. Contour bunding = make narrow embankments at intervals across the slope
  4. Graded bunding = channel terracing
  5. Bench terracing = a series of platforms with vertical drops along contours.
  6. Contour trenching = excavation of trenches across the slopes

III. Other Methods

  1. Gully plugging protects the gully beds by slowing down run-off water.
  2. Watershed treatment aims to increase vegetation cover
  3. Stream bank stabilisation uses trees and bushes on embankments
  4. Saving coasts = constructing off-shore breakwaters, sea walls and groynes.
  5. Controlling landslides
  6. Land capability classification

Soil Salinisation


Infiltration causes rise in water table-the farmer irrigates the field- causes waterlogging due to high water table and inability to infiltrate-evaporation allows salt to remain in the field.


  1. Yield lowered
  2. Crop choice limited
  3. Poor fodder quality
  4. Obstruction in construction


  1. Providing drainage
  2. Minimise water application
  3. Salt tolerant vegetation
  4. Use of gypsum
  5. Flooding the fields