A number of California avocado growers are experimenting with a high-density planting technique that can significantly increase the number of pounds they produce per acre while speeding up the picking process.
It's a system that has been used by the apple industry for about 30 years, said Tim Spann, research program director for the Irvine-based California Avocado Commission.
Using the high-density method, growers plant up to 400 avocado trees per acre on 10-foot by 10-foot blocks per tree - about four times the usual 110 trees per acre they plant on 20-foot by 20-foot blocks.
Growers cap the height of the tree at about 8 feet. Most avocado trees are about 35 feet tall.
The shorter trees can be picked from the ground - no need to use ladders - which makes harvesting faster and easier.
For the past three years, the commission has funded a project through which Gary Bender, farm adviser emeritus for the University of California Cooperative Extension, compiles data to evaluate the technique.
Under the high-density planting program, growers can now produce, on average, 25,100 pounds per acre compared to 7,000 pounds per acres for conventional groves, he said.
"We're significantly above the county average yield," he said.
Even in previous years with younger trees, Bender said yields averaged about 15,000 pounds per acre.
The labor cost of picking fruit in a high-density orchard drops from 25 cents per pound to 4 cents, he said, which is a bargain even with the need for additional pruning and other management practices.
But California avocado growers are at a disadvantage when they implement the program compared to growers in other places and compared to those who produce other fruits, Spann said.
Apple growers can control the height of their trees by using size-controlling root stock.
"We don't have that for avocados," Spann said.
In Chile, where some growers have been using the process for perhaps 10 years, they can use plant growth regulators that are sprayed on the trees or injected through the irrigation system.
That's not something that is available in California, and Spann said it's unlikely that the California Department of Pesticide Regulation would allow the growth regulators to be registered.
Instead, growers have to maintain tree size through cultural practices, like pruning or adjusting the spacing between trees.
Spacing trees closer together helps control growth by crowding them so they are competing more for available resources, such as water, he said.
Long term, breeders may be able to develop a tree that will work with high-density formats, Spann said.
Rankin McDaniel, owner and president of McDaniel Fruit Co., Fallbrook, Calif., said he's looking at the process, which also is used in Peru and Israel.
"Yields per acre need to increase for California to continue to have the ability to compete with production costs per acre in the global community," he said.