What happens when an orchard’s life is over?
Currently, many growers destroy the trees and start again with the soil.
Brent Holtz, county director and farm advisor in San Joaquin County for the University of California Cooperative Extension thinks the trees shouldn’t disappear from the picture.
“As growers you spend 25 years growing that tree,” he said to an audience in Modesto this year.
Holtz’s solution: by chipping trees on the spot, nutrients stored up over decades can be returned to the soil.
He began work testing the idea in 2008, when he and “The Almond Doctor” David Doll tested a piece of rock crushing equipment, the Iron Wolf.
Their experiment compared burning the trees versus chipping them with the Iron Wolf.
The result? The researchers didn’t see a noticeable difference in trump circumference, any noticeable difference in stunting.
The added benefit to chipping trees on site is that it creates a use for the trees, which haven’t had a ready outlet since electricity cogeneration plants around the state began shutting in 2015 or so.
Reusing trees on site saves the cost of orchard removal, which can be $500 an acre, Holtz said.
The UC research took place at Tallerico Orchard.
As seen in the chart above, the year after burning or grinding nutrients are more plentiful in the burn group. But by two years after orchard recycling, the grinding orchards have significantly greater nutrients in most major categories.
“In 2014, 2015, and 2016, we started seeing significant difference in trunk thickness for the trees in the grind area,” Holtz said. “There was always a slight increase in yield for the grind treatment over the burn.”
Beyond that, Holtz said there’s been less bud failure in the grind area than the burn area.
His team believes that improved organic matter in the soil is helping with water stress.
“We’ve seen an increase in soil organic matter, in carbon, in nutrients,” Holtz said. “We’ve seen a slight increase in orchard productivity.”
To find out more about orchard recycling, see this presentation by Holtz.