Fruit thinning strategies: The combination of heavy thinning and water deficits is a strategy that can be employed during water restrictions.
Water vs apple crop (part 2)
(Continued from last issue)
Market fruit size can be maintained, but yield will be substantially reduced.
For example, a market fruit size (e.g. fruit weight at 80 per cent of maximum size) with 50 per cent less irrigation is possible if trees are thinned to 20 to 25 per cent of the standard crop load.
Overseas data* was used to construct the response of fruit size and yield to a range of water deficits and crop load shown in Figure 4. The important points in this figure are:
The relationship between fruit size and yield is determined by crop load.
Yield increases with crop load up to the biological maximum in an orchard. Further increases in crop load have no impact on yield.
Fruit size rapidly declines with increases in crop load when the maximum yield is reached.
Fruit size and yield decrease with increasing water deficits irrespective of crop load.
The effects of water deficits on fruit size are much less with heavy thinning.
Thin early in the season
Thinning early in the season is recommended.
Base the level of thinning on fruit set and the outlook for irrigation water allocations. (Continued next issue)
See this article in Tree Fruit Nov 2019