Theory question 104
Soil Erosion and Conservation(a) Define soil erosion.
(b) List four factors that influence nutrient availability in the soil.
(c) Explain two roles of each of the following factors in soil formation: (i) climate; (ii) living organisms; (iii) topography;
(d) State four problems associated with overhead irrigation.
Show the model answer
(a) Soil erosion is the wearing away and removal of the topsoil by water, wind or other agents
(b) Any four: soil pH; leaching; organic matter content; soil texture; soil moisture; soil micro-organisms; temperature and aeration; cation exchange capacity
(c)(i) Climate: rainfall supplies water for chemical weathering and leaching; temperature changes crack rocks and speed reactions
(ii) Living organisms: roots break rocks and add organic matter; animals and microbes mix soil and decompose remains into humus
(iii) Topography: steep slopes lose soil by erosion giving shallow soils; low-lying areas collect deposits and may be waterlogged, giving deep soils
(d) Any four: high cost of equipment and running; needs pumping/pressure; water lost by evaporation and drift in wind; wets leaves, encouraging fungal diseases; can wash off sprayed chemicals; may cause erosion or crusting; needs clean water free of debris
Two roles for each soil-forming factor.