When an orchard is removed for replanting, the trees are usually uprooted, chipped and hauled to a biomass plant. However, burning the wood in a cogeneration plant removes carbon from the orchard and biomass plants are becoming fewer and farther from farms.
One alternative is grinding up the trees and incorporating the wood into the soil in the orchard. UC Agriculture and Natural Resources (UC ANR) scientists have been studying the effects of incorporating the wood chips into the soil since 2008.
“A lot of growers feared if we added that much carbon to the soil, the microbes breaking down the organic matter would tie up nitrogen and the trees would be stunted,” said Brent Holtz, UC ANR Cooperative Extension advisor. “But the research results suggest that the trees will do just as well or better in the presence of the additional organic matter.”
For the 2008 study, an IronWolf machine was used to grind up whole stone fruit trees and bury the organic matter in the soil in some plots. For comparison, the researchers burned trees and spread the ashes in the soil of other plots. Holtz compared the nutrient availability in the soil and health of trees planted in the research plots.
In a new study, Holtz hopes to compare the effects of using the IronWolf to recycle an almond orchard to using a large tub grinder, which leaves much finer particles of wood.
Holtz invites growers and other interested people to watch the IronWolf 700B, a newer version of the machine used in 2008, grind up almond trees in Chowchilla on Feb. 16 at 10 a.m.
“There has been increased interest in the project because of the closure of many of the biomass plants statewide. They used to take the debris of removed orchards,” said Holtz. “The purpose of this demonstration is to see if this method of orchard removal will be competitive with the tub grinding process, and become an economically viable alternative that improves soil organic matter and fertility.”
WHO: UC ANR Cooperative Extension advisors, growers, IronWolf equipment representatives.
WHAT: Watch a 100,000-pound machine push, grind and incorporate whole almond trees into the soil.
WHEN: 10 a.m., Tuesday, Feb. 16, 2016
WHERE: AgriLand Farming, 20875 Avenue24, Chowchilla, CA 93610