Pollination as a controlling factor in almond yield (AL14004)
What was it all about?
Almond trees require pollination to produce nuts. Less is known regarding how pollination interacts with other resource constraints to determine quantity and quality of nut production.
The research team conducted a three-year study to observe an almond trees’ response to consistently high levels of pollination (achieved by spraying pollen).
Firstly, the researchers wanted to determine if resource availability such as light and leaf area influenced flowering and fruiting at the spur level. Data gathered at the spur level is useful for understanding the potential mechanisms behind resource trade-offs when scaling up to the whole tree level. Each season the team tagged, hand pollinated, and followed flower spurs in different positions in the tree canopy to observe pollination effects at the spur level.
The data confirmed what the research team had expected - that spurs in higher light environments supported more nuts. Interestingly, production of a large number of nuts did not lead to smaller nuts. That is, there was no detectable size versus nut number trade-off at the spur level.
Secondly, pollen was collected from bee hives and applied in suspension (with boron added to support pollen viability) onto flowers across entire trees, to simulate maximum whole-tree pollination. Trees were sprayed twice, at 45 to 65 per cent and again at 90 to 100 per cent bloom.
The researchers found that whole tree pollination using sprayed pollen raised whole tree yield above that of non-treated trees by up to 15 per cent in some, but not all years. The relationship between pollination and fruiting depended on the light environment in that part of the canopy.
This research was designed to answer important questions about constraints to nut production, and how they interact with pollination. However, all the experiments conducted in the study strongly indicated that increasing pollination rates will increase yield, without compromising quality.
The foundation for boosting nut production under current pollination practices is to maximise flower production. Even though there may appear to be ‘surplus’ flowers, the data shows that on average, spurs with more flowers make more fruit.
This project has been funded by Hort Innovation
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