Agronomic Practices for Control of Soil Erosion (Water and Wind)
Among the different methods of erosion control, agronomic practices are considered effective and are usually given precedence because they are less expensive and deal directly with reducing raindrop impact, increasing infiltration, reducing run off volume and decreasing wind and water velocities. It is also easy to fit them into existing farming systems.
Agronomic practices used in erosion control include:
- Maintenance of high soil fertility
- Mulching
- Crop rotation
- Contour tillage
- Strip cropping
- Fallowing
- Alley cropping and
- Minimum tillage
1. Maintenance of High Soil Fertility
Continuous maintenance of ground cover in addition to high organic matter helps to conserve soil and prevent erosion.
It is believed that wise use of fertilizers, lime and manure increase the fertility of the soil which enhances proper plant growth leading to bumper harvest and an insurance for maximum ground cover.
2. Mulching
Mulching protects the soil surface from the direct impact of rain drops. The raindrop on bare soil tends to break soil aggregates apart and produce a crust of paddled soil. Such crusts have low permeability that reduce infiltration and increase run-off.
Maintenance of cover like the use of mulching materials at all times reduces crust formation, increases permeability and consequently there will be little run-off and erosion. This is one of the major crop management practices used in the control of soil Erosion.
3. Crop Rotation
Crop rotation which is a systematic sequence of planting one crop (of different morphology and nutrient requirement) after another, helps to maintain a better soil condition, to absorb water, when grass legume crops are included in crop rotations than the continuous mono-culture farming.
In addition to ensuring quick and efficient ground cover, legumes, have abundant vegetative growth which provides large quantity of crop residue to protect the soil surface in addition to enriching the fertility of the soil.
4. Contour Tillage
This is the cultivation of a sloppy small piece of land with ridges made across the slope rather than along the down.
Contour farming is adopted on a sloppy land and it is mainly done to reduce soil, water and nutrient losses. If done properly, it serves as an obstruction to the flow of water down the slope. Such restricted water subsequently infiltrates into the soil thus minimizing run-off and erosion.
5. Strip Cropping
Strip cropping is used on a sloppy land also. In this case the entire field is divided into series of strips separated by uncultivated bunds.
The system is called contour strip- cropping when the strips are laid out on the contour.
The crop is grown on strips which alternate with the strips of grass– legume.
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x–x– x–x– x–x– x–x– x–x– x–x–) Maize strip
x–x– x–x– x–x– x–x– x–x– x–x–)
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………………………………………) Grass/Legume strip
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x–x– x–x– x–x– x–x– x–x– x–x–)
x–x– x–x– x–x– x–x– x–x– x–x–)
x–x– x–x– x–x– x–x– x–x– x–x–) Maize strip slope
The water flowing across the strip of grass legume spreads across the strip due to its reduced velocity and much of the suspended silt is deposited between the grass blades at the top end of the strip.
Some of the clean water percolates into the soil while smaller portion of the run- off water reaches the lower end of the strip. Therefore, water moves out more slowly from the protective strip (Grass-legume strip) than it enters it.
Read Also: Definition of Water and Wind Erosion
6. Fallowing
Fallowing is an age long method of protecting the soil from physical, chemical and biological degradation.
This is the practice of abandoning a piece of land (after a long period of cultivation) to regain its fertility status after which it is now used again for another period of cropping.
Soil fertility maintenance is through the long fallow period. A fallow period is the number of years a piece of land that had been under cropping is allowed to revert to bush//forest.
Fallowing is a means of storing water in the soil from one year to the next, protects soil from erosion and helps to restore soil fertility.
7. Alley Cropping
Alley cropping, a promising system developed over the last several years, consists of growing rows of food crops between deep rooted trees.
The trees are pruned or pollarded at regular intervals to control shade and to produce mulch materials that are spread on the cultivated land between the rows.
Where this is practiced, this association of plants has maintained excellent continuous productivity and fertility maintenance. Leguminous tree crops are preferred because they can tap atmospheric nitrogen into the cropping system.
In alley cropping both the fallow and the cropping period are integrated at the same time. In addition to erosion control this system has an added advantage of recycling soil nutrients more especially if legumes shrubs are used.
8. Minimum Tillage
The conventional tillage operations of ploughing, harrowing and ridging usually lead to increased soil compaction which eventually reduce infiltration and encourage run-off and erosion.
Minimum tillage system (currently described as conservation tillage) eliminates all tillage operations except planting, and has the following advantages:
- Reduces the rate of erosion.
- Conserves water due to surface cover of plant residues.
- Reduces the cost of production and
- Increases crop yield.
Read Also: Factors that Determine the Amount of Wind Erosion