In Water and nutrient Losses we learnt how water and nutrient losses occur and the factors governing them. In this Writeup You shall Consider how to prevent and control these losses.
Prevention and Control of water Vapour Losses
1. Mulching - a mulch is any material such ad straw, leaves , saw dust or plastic film spread over the soil to reduce or prevent evaporation.
2. Crop cover - Keeping a Dense crop cover, such as by close spacing of crops, will reduce direct evaporation from the soil. Removal of weeds by cultivation or killing them with herbicides will eliminate loss of water by transpiration from the leaves of such weeds.
Prevention and control of liquid water losses
1. Organic matter - incorporation of organic matter In the form of crop residue, green manure or farmyard manure will improve the soil structure and increase permeability. Organic matter will also increase the water holding capacity of sandy soils and, therefore, reduce deep percolation.
2. Sub soiling - This is the breaking of compact subsoil without turning , using a special type of implement (chisel). This will improve the rate at which water penetrates the soil and reduce runoff.
Prevention and control of soil and nutrient losses Nutrient losses
All measures taken to control water losses by deep percolation will also control nutrient losses through leaching. Similarly measures that control runoff will control losses of nutrients with the runoff water. Other methods that can be used to control loss of nutrients from the soil include:
Avoiding burning , Returning crop residues to the soil, controlling erosion.
Soil Losses
The prevention and control of soil losses depend on the type of erosion. Erosion is the loss of the surface soil due to washing away by runoff water or blowing away by wind. These are called water and wind erosion respectively.
1.Water erosion is of three types.
i. Sheet erosion : it is the removal of fairly uniform layer of soil from the land surface by runoff water. The effect of raindrop splash AIDS sheet erosion in that the soil is loosened and becomes easier for runoff water to wash it away.
ii. Rill erosion : it is the process by which soil is removed through numerous small channels. This type of erosion accompanies sheet erosion. Both sheet and rill erosion can be controlled by :
(a) Contour Cropping - Planting crops along the contour so that they cut across the slope. This could be in the form of contour strip cropping or contour furrowing.
(b) Terracing - building terraces along the contours will reduce the slope length. The water is caught in the terrace channels and conducted away from the field at a gentle grade.
(c) Gully erosion - When rill erosion is not controlled, the small channels become bigger until they form gullies. More soil is lost in the process. This type of erosion can only be controlled with heavy earth moving machinery.
2. Wind erosion is most common in dry areas but can also occur in humid regions where there is a well marked dry season. The factors governing wind erosion are:
I. Moisture - The drier the soil the more easily it is carried away by the wind.
ii. Speed of the wind - Soil loss increases as wind speed increases.
iii. Surface conditions - Wind erosion is greater when the soil surface is smooth.
iv. Soil characteristics - Loose sandy soils are more easily eroded by wind erosion than clayey soils.
The measures to control wind erosion are :
(a) Leaving a vegetation cover on the soil such as cover crop or stubble mulch which is the remains of the previous crop after harvest.
(b) Wind breaks - a row of shrubs planted perpendicular to the wind direction.
(c) Tillage - To provide a rough surface condition that reduces the wind speed at the soil surface.
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