Theory question 103
Soil Fertility and Plant Nutrition(a) State four characteristics of a fertile soil.
(b) Discuss briefly three factors that affect land availability for agricultural production in West Africa.
(c) State four benefits of draining farm lands.
(d) List two sources of soil nitrogen.
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(a) Any four: contains enough of all nutrients in available form; good water-holding capacity and drainage; good aeration and crumb structure; suitable pH; deep enough for roots; rich in organic matter and organisms; free from toxic substances and pests.
(b) Any three discussed: population pressure – more land for houses and less for farms; land tenure system – fragmentation and insecurity; topography – steep or swampy land is hard to farm; soil type/fertility; climate; industrialisation and urbanisation; government policy/land use act; erosion and pollution.
(c) Any four: removes excess water and improves aeration; allows roots to grow deeper; raises soil temperature; increases activity of useful organisms; reduces leaching losses and toxic substances; makes land workable earlier; reduces diseases.
(d) Any two: fixation by legumes/rhizobium; free-living nitrogen-fixing bacteria; lightning; organic matter decomposition; fertilizers; animal manure.
In (b) explain how each factor limits the land available.