Avocado Production in Asia and the Pacific - United Nations in ...

is good practice to cover the one square metre planting site with an open mulch, which
reduces water loss and suppresses weed growth.
5. CARE AND MANAGEMENT OF ORCHARDS
5.1 Training and pruning
There is little tree training practised on avocados during their establishment years
apart from tipping the central shoot to encourage branching when trees are received from the
nursery. Tipping growing points of trees in their second year to increase tree complexity is
carried out by some farmers but there is little evidence of benefits.
Controlling tree growth in mature orchards remains the biggest challenge of orchard
management. Being terminal flowering trees, avocados need to grow each year in order to
remain productive, hence trees become larger. To maintain orchard access between rows,
major limbs are periodically removed, cutting back to the main trunk. Similarly, to contain
tree height major limbs are lopped from the top of the tree when necessary. In some
orchards, trees are not pruned at all until their size is so great that they are uneconomic to
manage. They are then stumped to approximately one metre high and allowed to regrow.
After this treatment they are back in full production within two years.
Current research is investigating the use of mechanical pruning equipment to
hedgerow trees at strategic times during the summer. Regrowth is then sprayed with a
growth inhibitor (uniconazole) to suppress shoots and encourage floral initiation. Conclusive
results from this research are not yet available.
5.2 Crop nutrition
Crop nutrition is based on critical leaf levels to predict requirements for the following
season. Critical leaf levels established for avocado are presented in Table 1.
If required, most nutrients are applied in the spring or summer, usually by fertigation.
Generally, however, nitrogen is applied after the spring fruit drop is completed. This is to
reduce the risk of promoting too strongly spring shoot growth at the expense of the
developing fruit. AVOMAN, a computerised orchard management programme, provides a
customized nutrition programme for each block of trees in an orchard integrating the past
cropping history of the trees, current crop load, rainfall and nutrient status.
9