(a) State three methods of irrigating a small nursery. (b) Enumerate three factors to be considered in the choice of each of: (i) surface irrigation method ...

(a) Three methods of irrigating a small nursery [3 marks]

• Watering with a watering can (hand watering).
• Sprinkler (overhead spray) irrigation.
• Drip (trickle) irrigation, or the use of a hose.

(b) Three factors considered in the choice of each method [6 marks]

(i) Surface irrigation:

• The topography of the land (it must be fairly level/gentle slope).
• The type/texture of the soil and its infiltration rate.
• The quantity of water available and the type of crop grown.

(ii) Sub-surface irrigation:

• The depth and nature of the water table.
• The soil type and its capacity to move water upward (capillarity/permeability).
• The cost of installation and the quality of the water (it must be free of salts to avoid salinity).

(c) Two advantages of sub-surface irrigation [2 marks]

• It supplies water directly to the roots with little loss through evaporation, so water is conserved.
• The soil surface stays dry, which reduces weed growth and the spread of foliar (leaf) diseases.

(d) Five ways of reducing build-up of diseases on an irrigated farm [5 marks]

• Practise crop rotation to break the life cycle of pathogens.
• Use clean, disease-free (treated) planting materials and resistant varieties.
• Ensure good drainage so that the land is not waterlogged.
• Keep the farm clean by removing and destroying infected plants and weeds (field sanitation).
• Use clean irrigation water and apply appropriate chemicals/biological control against pests and diseases.