WAEC Agricultural Science 2024 Theory — Question 5

Model answer

(a)(i) Removal of excessive vegetation: allows sunlight to reach the bottom of the pond for growth of phytoplankton; prevents breeding of fish pests; ensures adequate supply of dissolved oxygen; prevents breeding of fish diseases. (ii) Removal of silt: makes the pond water clear/reduces turbidity; facilitates free movement of fish; maintains normal depth of the pond; ensures adequate supply of dissolved oxygen. (iii) Supplementary feeding: promotes rapid growth of fish; improves the health of fish; provides variety of feeds to fish/balanced diet/adequate nutrition. (iv) Fertilizer application: encourages growth of phytoplankton; provides nutrients to fish; improves growth of fish in ponds. (b) Conditions necessitating culling: low productivity/poor feed conversion; old age; aggressiveness; lameness/parturition problems; diseases/severe injury; egg pecking/sucking; poor mothering/piglet eating; reproductive failure/sterility; cannibalism. (c) Effects of excess nitrogen in soil on crops: causes excessive vegetative growth; decreases reproductive growth/delays fruiting; weakens plant stems; causes lodging in crops; reduces resistance of crops to diseases; reduces the yield of some crops.