Avocado farmers may be able to stabilise their year-on-year harvest and returns with the introduction of new technology. This will lead to better planning, decision-making and greater security.
According to business development manager of plant nutrition at Laeveld Agrochem, Nico Claassens, avocado and many other crops such as citrus, nuts and deciduous fruits adapt an alternative bearing cycle - an on-crop/off-crop cycle, alternating each year. “This means that the return can fluctuate by more than 50% between an “on-year” and an “off-year,” says Claassens.
The balance determining alternating behaviour
New research by the University of California, Riverside, indicates that the fluctuation in the hormone balance between the cytokinins and the auxins in the plant plays the dominant role in determining the alternating behaviour of crops like avocados. At first, it was thought that it was only the carbo-hydrates in the plant that was the primary reason for this tendency and much research was done to ascertain how to stabilise the carbohydrate reserves or to top them up to that of an “on-year” level.
Cytokinins and auxins are both plant growth hormones which control the vegetative and reproductive growth of the plant. Cytokinins are produced in the underground parts of the plant and move upwards to stimulate lateral growth. Auxins are mainly produced in the plant’s seeds and move downwards to restrict lateral growth.
Thus, the development of the plant is controlled by the balance between the two hormones. An imbalance results in the plant when the one hormone overrides the working of the other. In the event of the auxin being overridden, the growth of both the bud and racemes is stunted which has a direct impact on the productivity of the tree.
The following steps are recommended to restrict alternating behaviour and to ensure more stable harvests:
- Apply the correct pruning methods to stimulate new bud growth.
- Get rid of excess fruits through pruning or fruit thinning.
- Harvest the trees completely, as soon as possible.
- Fertilise the tree according to the current season’s potential crop yield.
- Supplement soil fertilisers with foliar feeding – which includes both plant nutrition elements and plant growth stimulants – during the critical phenological phases.
- Use Plant Growth Regulators (PGRs), such as cytokinin, to reset the hormone balance to a pro-fruit set phase. Fortunately, technology has advanced to such an extent that PGRs can be artificially added. The type and timing of the application are important to ensure the required result.
