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Cutting labor and input costs while increasing fruit size, yield and quality, what’s possible and what’s not? . Ted DeJong. National farm wages have increased by ~100% over 20 years.
This may be even higher in California and does not include increased costs related to labor management and reporting.
In the same ten year period average US farm fuels expenditures increased by ~59%.
It is interesting there has been a consistent marketing trend toward packing larger and larger sized fruit over the past 20 years.
This has been done by preferentially packing larger sized fruit and discarding more fruit in the small size categories.
Lopez, Johnson and DeJong, California Agriculture, 2007
Other things being equal, fruit size is inversely related to yield and the relationship is not linear.
To make matters worse the previous figure only showed the relationship between average fruit size and yield. Fruit sizes on a tree are normally distributed so there are always some fruit on the tree that will not make size and at higher crop loads a greater proportion of the crop will not make acceptable size.
But other things are not always equal. In years with warm springs fruit development rates are more rapid and this means fruit growth rates per day must be greater to make up the same amount of size in a shorter amount of time. This is not possible especially if the fruit are not thinned in time.
Thus, fruit size at pit hardening will be smaller and this will very likely carry forward to harvest.
The next few slides will demonstrate how this happens.
It all follows from the Relative Fruit Growth Model that we have developed for peaches.
If we use the RGR functions shown on the previous slide to project potential fruit dry weight growth for three contrasting seasons we see substantial differences in the timing of potential fruit sink demands for carbon.
The differences between seasons is even more apparent when potential absolute fruit growth rates of individual fruits are calculated for the first 50 days after bloom.
When the individual fruit growth demands are compounded by pre-thinning crop loads during the first 50 days after bloom, the differences in potential carbon demand by the fruit among years are really apparent.
We have shown experimentally that early thinning can increase fruit size and yield.
Thinned 90 days after bloom
Thinned 60 days after bloom
Thinned 30 days after blooom
Mean fruit dry mass (g fruit -1)
Thinned at bloom
Day of year
We obtain similar results when we use a crop canopy simulation model.
The machine on the left is used to reduce flowers at bloom.
The machine below is used in New York and is like what is being tested in California now for olive harvesting.
After 12 growing seasons trees on Controller 9 had trunk circumferences (cm) that were nearly the same as trees on Nemaguard but trees on Hiawatha and Controller 5 were substantially smaller. Trunk circumferences of the KAC-V trees were also smaller than open vase trees.
Differences in vegetative vigor (as reflected by pruning weights) among trees on different rootstocks were apparent very early in the trial and remained fairly consistent. The differences in vigor are essentially the selling points of the size-controlling rootstocks.
But, based on the knowledge that we now have, I don’t see how it will be possible to substantially increase profitability of producing fresh market peaches, nectarines and plums in California without some strategic restructuring of the industry to increase the value of the fruit that is sold.
For processing peaches I believe you have the possibility to increase profitability if you concentrate on restructuring the orchards to decrease thinning and harvest costs while continuing to optimize all other management inputs and putting pressure on buyers for increases in price paid for your fruit.