(a) Discuss three effects of each of the following factors on crop production: (i) water; (ii) air; (iii) soil microbes. (b) List three edaphic and four climatic factors that affect crop productivity.
Explanation
(a)(i) Effects of water on crop production are: (1) Water dissolves soil nutrients for easy absorption by plant roots (2) Water is needed by plant for metabolism. (3) It is needed by plant in large amount in the physiological process of transportation. (4) Plants are protected from injurious effects of high temperature by water. (5) Water is needed for germination of seeds. (6) Water is needed for translocation of food substances in plants. (7) It helps to maintain turgidity of plant parts.
(ii) Effects of air on crop production are: (1) Air must be present in the soil for the respiration of micro-organisms which enhance crop growth through enhancing mineralization. (2) It provides a favourable environment for root development and the absorption of nutrients. (3) Air is needed for root respiration. (4) Seeds require air for germination. (5) Air supplies carbon-dioxide for photosynthesis.
(iii) Effects of soil living organisms on crop production are: (1) Soil living organisms help in the decomposition of soil organic matter. (2) Some soil living organisms involved in soil mineralization. (3) They improve soil structure, aeration and the rate of water percolation and infiltration of soils. (4) Some soil living organisms are involved in nitrogen-fixation in the root nodules of legumes. (5) Some microbes, e.g. nematodes, cause crop diseases. (6) Some cause loss of soil nitrogen through denitrification, 7) Some soil living organisms are involved in nitrification of ammonia to nitrites and nitrites to nitrate.
(b)(i) Edaphic factors that affect crop production are: Soil pH, soil structure, soil texture, soil consistency (ii) Climatic factors that affect production are: Rainfall, temperature, light, wind, altitude.