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A L M O N D O R C H A R D 2 0 2 5 G O A L S ZERO WASTE Almond Board of California 8 maximize all the good effects in terms of pest inactivation and plant nutrient accumulation in the soil, without going so far as to radically alter the soil properties to the extent where there is an inordinate amount of time for the trees to adapt." The ultimate proof, of course, will be in yields. Simmons hopes to continue working with Crowley to gather yield data as the trees mature. Irrigation drives costs Asked to compare costs of conventional fumigation to biosolarization, Simmons said he believes costs for biosolarization are comparable to fumigation in some cases but will vary depending on the specific orchard. A key aspect of that variance is irrigation – because biosolarization requires use of drip lines or tape beneath a plastic barrier, costs will depend on whether the orchard already has infrastructure to support drip irrigation, and whether the intent is to use that in the replanted orchard. Irrigation can be the single greatest cost related to biosolarization, he said, but if the infrastructure is already in place and going to be used in the new orchard, that potential cost is essentially nullified. Regardless of cost, Simmons advises growers who are interested in trying biosolarization to do so first on a small test plot of 10-to-20 trees with a replanted orchard. This will allow collection of data to better inform how to do this practice in specific soils and conditions on a larger scale. Interested growers should contact Simmons 2 or their local UC Cooperative Extension farm advisor to request assistance. Simmons also noted that while using almond hulls and shells as part of a preplant biosolarization strategy can provide benefits directly to almond growers, there is also a potential opportunity for hulls and shells to be sold for use in other crops as an alternative to conventional fumigants. With the support of ABC and the Western Center for Agricultural Health and Safety, that possibility is being explored. "While we've shown with this study that biosolarization can be used within the context of preplant operations for almond orchards, that is a very brief window in the life of an almond orchard," he said. "As such, we have started to look at biosolarization using almond hull and shell amendments for lettuce production, fresh market tomatoes, and berries." To learn more about this ongoing research, watch a short video featuring Simmons on the Western Center for Agricultural Health and Safety website. 3 2 Growers may reach Simmons at cwsimmons@ucdavis.edu. 3 https://aghealth.ucdavis.edu/research/pesticide-exposure During biosolarization, drip tape runs beneath a clear plastic tarp, allowing the grower to add moisture while sealing out air and allowing the sun to heat the soil. Using this method for as few as eight days can control soil pests without using fumigants. Photo courtesy of Chris Simmons "Soil disinfestation could become a good use of almond hulls and shells, particularly low-grade hulls and shells." — Guangwei Huang Photo courtesy of UC Davis