Theory question 103
Irrigation and Drainage(a) State five effects of each of the following practices on crop production: (i) Irrigation (ii) Drainage
(b) List four methods of surface irrigation.
(c) Give two main reasons why surface drainage is often necessary in crop production.
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(a)(i) Irrigation (any five): allows dry-season and all-year cropping; raises yields; softens soil for tillage; dissolves nutrients for roots; cools the crop; may cause salinity, waterlogging, leaching or spread of weeds and water-borne diseases
(ii) Drainage (any five): removes excess water; improves aeration for roots; warms the soil earlier; increases microbial activity and decomposition; lets roots grow deeper; prevents toxic substances building up; makes tillage and harvesting easier; reclaims swampy land
(b) Any four: flood (wild flooding); furrow; basin; border strip; check flooding
(c) Any two: to remove excess surface (rain or flood) water quickly and prevent waterlogging; to prevent erosion from run-off; to improve aeration and workability of the soil
Give both good and bad effects of irrigation.