Huge Yield Variability

Huge Yield Variability

Growers know that certain orchards are more productive than others, and that certain blocks within those orchards likewise differ. But researchers are learning that there are tremendous differences from tree to tree — as much as 40% — and they’re hoping that some day soon growers may be able to monitor those differences, boosting overall yields enormously.

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Pomologist Patrick Brown and colleagues at the University of California-Davis have been monitoring the yield of every tree in an 80-acre pistachio orchard for the past six years. Brown says the orchard, which is located near Kettleman City, CA, is one of the best orchards in the region. But even in such a well-managed orchard, the yields among the 10,000 trees vary widely. “We’re seeing yield differences of 30% to 40% from tree to tree,” he says. “But you would never know it’s there unless you monitor the harvest precisely.”

While pistachios have greater yield differences than other nut crops, Brown believes the differences largely hold true for crops such as almonds as well. They haven’t been able to measure the differences in almonds because they don’t have the necessary equipment. The machine they use for monitoring pistachio yields not only can measure each tree, but can do so without slowing down harvest. But Brown believes that when they are able to measure almond yields as precisely, growers will be similarly shocked at the variability. “Unless you measure every tree,” he says, “you simply don’t know it’s there.”

Nuts To Go High-Tech

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Because that information hasn’t been available in the past, Brown is not surprised by how poorly the demand for high technology fared in a recent survey of growers he and his colleagues conducted. The exhaustive survey of 1,800 randomly selected almond and 300 pistachio growers from throughout California sought to determine their priorities for further research to optimize the management of nutrition in almond and pistachio production. The survey, which included focus group interviews, was prompted by the fact that it’s long been known in the nut industry that long-established nutrient standards are outdated. By surveying growers, researchers could not only identify where the weaknesses exist in current knowledge, but could find out exactly what growers seek in the way of further research.

In the survey, the lowest priority identified by growers was in the use of remote sensing and automated nutrient status management. Other high-tech solutions that ranked near the bottom (see “Priorities In Future Research”) were precision agriculture and the optimal use of fertigation systems. Brown believes those results are due to the fact that the companies who have developed such high-tech equipment have focused their efforts on such large program crops as corn and soybeans. But that’s changing, says Brown, as companies see the advantages of applying the technology to more high-value fruit and nut crops.

“It’s intriguing that it’s been applied in crops such as wheat, because the margins are so small. It makes more sense in high-value crops where the potential for higher profits is huge and it has long-term effects,” he says. “The payback for investment in tree crops is much bigger than in soybeans and corn crops.”

Cutting Inputs

As growers become more familiar with such high-tech equipment, Brown says he has no doubt that they will be quick to adopt new technology. He notes that the number-one priority identified in the survey was fertilizer application timing, which shows that growers have come to realize just how critically important timing is in fertilizing. It used to be that growers would apply a lot of fertilizer at one time in the fall, but as research has revealed that it’s critical to make the nutrients available when the trees need it — about 20% to 30% in spring, 30% to 40% in summer, and the remainder at or just after harvest — growers have changed their practices accordingly.

Growers are absolutely correct in believing more research in the area of application timing is necessary, says Brown, and not just because it helps to increase yields. Growers are able to use as little as possible of the inputs, which have been skyrocketing in cost of late. In addition, in maximizing availability to the trees, growers are also minimizing availability to the environment, a win-win situation. In fact, Brown recently returned from a tree nutrition conference in Portugal, where researchers remarked to him how savvy U.S. growers were to realize how their applications could potentially impact the environment.

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