Theory question 103
Crop Husbandry(a) Discuss the cultivation of cassava under the following headings: (i) soil requirements; (ii) spacing; (iii) one disease; (iv) one pest.
(b) Differentiate between natural pasture and artificial pasture.
(c) Explain the term disease as used in crop production.
(d) State Mendel's law of independent assortment of genes.
(e) Explain the term regeneration as a forest management practice.
(f) State five effects of deforestation.
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(a)(i) Deep, loose, well-drained sandy loam soil, fairly fertile; avoid waterlogged soils.
(ii) About 1 m × 1 m (or 0.9 m × 0.9 m).
(iii) Disease (one, with cause, symptoms, control): cassava mosaic disease – virus spread by whiteflies; mottled yellow leaves, leaf distortion, stunting, small tubers; control by resistant varieties, clean cuttings, uprooting and burning infected plants. (Or cassava bacterial blight.)
(iv) Pest (one, with damage and control): cassava mealybug – sucks sap, causing bunchy top and leaf fall; control by biological control (parasitic wasp), resistant varieties, insecticides. (Or green spider mite, grasshoppers, rodents.)
(b) Natural pasture grows on its own without being planted, contains mixed and often low-quality species; artificial (sown) pasture is planted and managed by man with selected grasses and legumes of high quality and yield.
(c) A disease is any harmful change in the normal functioning of a plant caused by pathogens (fungi, bacteria, viruses, nematodes) or by unfavourable conditions, which reduces growth and yield.
(d) When two or more pairs of characters are inherited, the members of each pair of genes separate (segregate) independently of those of other pairs during gamete formation.
(e) Regeneration is the renewal of a forest after trees have been felled, either naturally (seeds, coppices) or artificially by planting seedlings.
(f) Any five: soil erosion; loss of soil fertility; loss of wildlife and biodiversity; desert encroachment; climate change/less rainfall; loss of timber and forest products; flooding; reduced water supply.
Give cause, symptom and control for the disease, and damage and control for the pest.