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Monday, Dec 4, 2023

Green Acres

Avocado farmers, struggling for years with soaring water prices, are starting to embrace a relatively untested planting method that could double their yield and might even curb water use.

Water prices are reaching up to $1,600 per acre-foot, making profits hard to come by for the water-thirsty crop. The value of the county’s avocado crop fell to $154 million in 2014, the latest figures available, from $198 million the year before. The drop was due to farmers cutting avocado acreage from 21,000 to about 18,000 acres as they replaced avocados with other crops.

The average yield for avocados is about 6,500 pounds per acre and farmers can use up to four acre-feet of water per acre. That means avocado growers need to get about $1 per pound just to break even and many are only getting 85 cents, according to Gary Bender, farm adviser emeritus at the University of California Cooperative Extension.

So some farmers are turning to a relatively untested method of avocado growing that promises to more than double yield using the same amount of water. Instead of planting about 100 trees per acre and letting them grow more than 30 feet tall, some farmers are packing in 400 trees per acre and trimming them no higher than eight feet. Initial results from a UC study recorded yields of 13,600 pounds per acre.

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Water use is even lower than normal because wind-driven water loss through high-reaching leaves is avoided by keeping the trees low to the ground, according to Bender, who is using less than three acre-feet of water per acre for his avocado study.

“This is a last gasp at improving yield,” Bender said.

Investment Decision

High-density planting has been considered by Southern California growers since the late 1990s, and is commonly used in Chile, but most farmers here still don’t use it. That’s partially due to the age of San Diego’s avocado farmers, who planted most of their crops in the 1960s through 1980s, according to San Diego Farm Bureau executive director Eric Larson. Older growers are not likely to make the considerable investment needed to cram in more trees, especially if they might not see a return for several years.

“Conversion percentage is probably in the single digits,” Larson said. He added that many farms are on rocky hillsides that can’t be planted any denser.

Al Stehly oversees about 500 acres of citrus and avocados as owner of Stehly Grove Management and has about six acres of avocados himself. He’s pushed all his clients to take up high-density planting since seeing the practice in Japan in the 1980s. The yield of about 15,000 pounds per acre for his acreage is worth the tradeoffs, including making it easier for thieves to snatch the low-hanging fruit.

“It’s a lot cheaper to pick per pound,” he said. “And avocados ripen after you pick them. Since it’s so easy to pick, you can pick multiple times a year and still have good product to sell.”

Sustainable in SoCal?

Enrico Ferro, owner of Ferro Orchard Advisors, has about 17 acres of high-density avocados in Valley Center. In addition to yields of 10,000 pounds per acre, high density planting has also cut his insurance costs — his workers no longer need to climb up 40-foot ladders to harvest.

But high-density planting is still risky, he said. Farmers need to quadruple their initial planting costs and there is not enough data to show conclusively that the method is sustainable in Southern California.

And there is another wrinkle. Because the trees are so close together, they need to be pruned regularly once they’re three years old to avoid shading each other out. But because avocado trees have traditionally been left to grow free, there isn’t any conventional wisdom about the best time or way to prune.

Cutting off fruiting wood will torpedo the next year’s harvest, so while the first few years may show promising results, such as a Temecula farmer who saw 32,000 pounds per acre, according to Bender, the real test is whether those results continue after pruning. That same Temecula farmer had barely any production after an early pruning.

“There’s never been a real good pruning method for avocados and everybody’s trying to find the best way without ruining production,” Ferro said. “The initial data looks really positive, but if you don’t stay on top of the pruning, then you lose that. It’s still experimental.”

Pruning Methods

Bender, who is overseeing the UC avocado study, is trying to pin down the best way to prune the trees. He’s comparing two methods: one in which all sides of the tree are pruned each year and its top is cut to eight feet, and another where he rotates which side is trimmed every year. The first harvest only came last year and that was before major pruning began, so it’s too early to tell which method will be more successful.

Conclusive results may take an additional five years, but Bender said he plans to share initial findings each year with farmers, many of whom are already stumping their trees just to cut down on costs.

“If I wait five years, I’m not sure we’ll have any growers,” he said.


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