(a) State five effects. of each of the following practices on crop production: (1) irrigation; (ii) drainage. (b) List four methods of surface irrigation. (c) Give two main reasons why surface drainage is often necessary in crop production.
Explanation
(a)(i) The effects of irrigation on crop production are: (1) Irrigation softens the soil for easy tillage operations. (2) It provides moisture in the soil for root absorption. (3) It reduces the amount of salts accumulated in the top soil, which could be harmful to crop plants. (4) It also cools the soil by reducing the soil temperature during the dry season when the soil temperature is very high and plant growth is thus improved. (5) Irrigation enables the crop to be well established even when rain is erratic. (6) It increases crop productivity or crop yield. (7) Irrigation provides humid environment for the breeding of pest and pathogens of crops. (8) It helps in the improvement of microbial decomposition of organic manure to release nutrients for crop plant. (9) Irrigation dissolves nutrients for root absorption. (10) It assists in facilitating crop production all year round. (11) Irrigation encourages the spread of weed seeds.
(ii) The effects of drainage on crop production are: (1) Drainage helps in reclaiming waterlogged soil for crop production. (2) Drainage improves the soil structure thereby improving the water holding capacity of the soil. (3) It improves soil aeration for good root respiration. (4) It gives suitable conditions for the growth of soil microbes responsible for the decomposition of soil organic matter which provides nutrients for plant growth (5) It helps to increase the soil temperature for the benefit of crop plants (6) Drainage also leaches excess salts from soil thereby preventing the death of plants arising from poisoning (7) It makes tillage operations easier. (8) It reduces the incidence of crop diseases. (9) It enhances harvesting of crops, especially swamp rice. (10) It enhances early planting of crops.
(b) The methods of surface irrigation are (i) Contour ditch (ii) border dyke (iii) border ditch (iv) furrow irrigation (v) basin irrigation (vi) wild flooding.
(c) Surface drainage is necessary in crop production because: (i) It removes excess water caused by heavy rainfall especially in heavy soils (ii) it is easier to construct (iii) Irrigation is cheap to establish and maintain (iv) It prevents accumulation of alkalis (v) It increases the activities of microbes in top soil (vi) It helps in the collection and disposal of surface run-off.