Theory question 102
Rocks and Soil Formation(a) Explain three roles played by each of the following factors in soil formation: (i) time; (ii) rainfall; (iii) parent material.
(b) Mention four principles which should be followed in a good crop rotation plan.
(c) Give five uses of forage crops.
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(a)(i) Time: the longer weathering goes on, the deeper the soil; older soils have well-developed horizons; time allows organic matter to build up and leaching to occur.
(ii) Rainfall: water breaks rocks (hydrolysis, solution); causes leaching of nutrients; moves particles (erosion, deposition); supports plants and organisms that form humus.
(iii) Parent material: decides the minerals and nutrients in the soil; decides texture (sandy or clayey); affects soil colour, pH and depth.
(b) Any four: deep-rooted crops should follow shallow-rooted ones; legumes should be included to add nitrogen; crops of the same family or with the same pests should not follow each other; heavy feeders should come first after fallow/manuring; include a cover/fallow crop to control erosion; crops should suit the soil and farmer's needs.
(c) Any five: livestock feed (grazing, hay, silage); cover crops against erosion; green manure; improve soil fertility (legumes fix nitrogen); mulch; roofing/thatching material; weed suppression.
Three roles for each factor in (a).