(a) List four soil conservation practices that can be used to control erosion on a gentle slope. [4 marks]
(b) Explain how each of the practices you have listed in 4(a) can be used to conserve the soil. [12 marks]
Explanation
(a)Soil conservation practices that can be used to control erosion on a gentle slope: (i) Terracing (ii) Contour ploughing (iii) Ridging across the slope (iv) Construction of drainage channels. (v) Cover cropping/Afforestation/High density planting. (vi) Strip cropping (vii) Mulching
(b) How each practice can be used to conserve the soil:
(i) Terracing:
-A practice in which the slope is broken into series of steps/platforms.
-Each platform/step is constructed along a contour so that each of them is on uniform height, but different from those above or below it.
It is done to reduce the length and gradient of slope and hence reduce the speed of run-off.
-Water collected on each gentle slope runs across the field rather than down.
-Each terrace has a drainage channel which empties into a grassed waterway which leads the water down the slope to nearby channel.
(ii) Contour ploughing
-The slope is first surveyed to locate contour points.
-Ploughing is now done along the contours joining all areas along each contour.
-These contours are running across the slope of the land.
- Plants are established along the contours and not across.
-An effective way of preventing soil loss and hence promoting soil conservation.
(iii)Ridging across the slope
-Flood water will normally run down along the slope of a land.
- Ridges constructed should be across the slope to block the run-off water.
- Such ridges will also help to trap the water into small reservoirs which will sink into the soil.
- Can be practised by every farmer without much -technical know-how.
(iv)Construction of drainages
-Drainages are means of getting rid of excess water in the field.
- Many types of drainages are available, they may be )pen channels or underground channels.
-pipes are laid along the slope to carry the water straight down into reservoirs below, thus preventing soil erosion
(v) Cover cropping/Afforestation/High density Panting
-The principle is not to allow the surface to be exposed to agents of erosion e.g. wind, water.
-The slope is planted with cover crops or other crops to trap/retard any run-off water.
-They also promote the percolation of such water which as been retarded in its flow.
-Planting of forest tree/other crop species to also trap and intercept water/dust from wind and thus protect the soil surface especially in the arid areas.
-Their leaves decay and enhance soil fertility, thereby encouraging more growth of other species.
(vi) Strip cropping
-planting of crops in rows along the contour interspersed by rows of uncultivated area/fallow, to retard water run-off across the slope. -planting of different crops with different growth characteristics in alternate rows along the contour and across the slope to check run-off .
(vii) Mulching
-Mulching is the act of covering soil surface with such
-Materials as d grasses, crop residues and polyethylene sheets.
-Reduces the the impact.of rain drops on soil.
-reduces the speed of run-off.
-Decayed, mulch improves soil structure and so help check soil erosion.