Fertiliser application and pruning of Hass and Fuerte avocado varieties.
To obtain maximum growth and optimum yields, it is important to supply the avocados with necessary nutrients. It is, however, dangerous to give excessive amounts on any size of trees at one time as it may cause root damage, leaf burn and defoliation.
The type of fertiliser to be used depends on soil pH. In the planting year, it is advisable not to top dress the orchard since this may retard root development during the first 4-5 months after planting.
After this period, 60g of 26 per cent of N fertiliser should be applied after every three months when the soil is moist. In addition, about 25kg of well-rotten manure should be spread around the trees after each year.
The following are recommendations for N and P fertilisers to be applied each year (CAN and SSP) per tree:
1st year after planting: 60g CAN + 250g SSP
2nd year: 85g CAN + 500g SSP
3rd year: 500g CAN + 750g SSP
4th year : 750g CAN + 750g SSP
5th year: 1kg CAN + 750g SSP
6th year: 2kg CAN + 1kg SSP
7th year: 3kg CAN + 1.5kg SSP
8th year: 4kg CAN + 2kg SSP
9th year: 5kg CAN + 2.5kg SSP
10th year: 6kg CAN + 3kg SSP
The CAN should be applied in splits. The use of farmyard manure is particularly strongly recommended because it improves the physical condition of the soil and promotes the adsorption in the soil and uptake by the plant of micronutrients.
Avocado trees also have a very high requirement for potassium, magnesium and zinc. Measures should therefore be taken to supplement these when they fall short.
Pruning: Normally, no pruning is required besides the removal of broken and diseased branches and trimming those touching the ground.
Sucker growth is checked to remove shoots coming out of the rootstock.
Department of Crops, Horticulture and Soils, Egerton University.