WAEC Agricultural Science 1997 Theory question 102

Any four with uses, merits and demerits: human (manual) labour – cheap, flexible but slow, tiring; animal power – bulls, donkeys, camels for ploughing and transport, give manure but need feeding and care; mechanical (engines/tractors) – fast, large areas, but costly and need skilled operators; electricity – processing, pumping, lighting, incubators, but not available in many rural areas; wind – windmills for pumping water and winnowing, but unreliable; water – water wheels, hydro-power; solar – drying crops, solar panels

Explain how each is used with one advantage and one disadvantage.