Issue link: https://www.e-digitaleditions.com/i/1310869
A L M O N D O R C H A R D 2 0 2 5 G O A L S ZERO WASTE 7 – it's also better for the soil. Simmons said he measured an additional 1.5% of biomass (dry weight basis) in the top seven inches of the orchard's soil. Crowley said the difference was obvious. "When you touch the dirt, you can feel it – it's rich, it's fluffy, it's dark," he said. "As a grower, you just love that." "There are remarkable benefits to soil health for the grower as a result of adding organic matter," Simmons said. "Land application of this material isn't new, and there are benefits to the soil by just mulching organic matter on the surface or tilling it in, similar to methods used in Whole Orchard Recycling. What we've done with biosolarization is extract more value beyond what you would see with conventional broadcasting on the soil to achieve results that extend beyond pest management and push almond coproducts to work harder for the industry, providing the maximum value possible." Soil benefits beyond biosolarization The Almond Board of California (ABC) and Western Center for Agricultural Health and Safety funded this research to help ensure fumigant alternatives are available to growers and that valuable uses for almond hulls and shells are identified and maximized, according to Guangwei Huang, associate director of Food Research and Technology at ABC. "Soil disinfestation could become a good use of almond hulls and shells, particularly low-grade hulls and shells," Huang said. Huang added that Simmons' work at Crowley's Chico orchard demonstrates similar findings to that of other researchers such as Greg Browne, Ph.D., a USDA Agricultural Research Service scientist stationed at UC Davis. In other work supported by ABC, Browne has shown that the process he calls anaerobic soil disinfestation (ASD) can be used to battle Prunus Replant Disease and soil pathogens. Similar to biosolarization, ASD also involves the addition of organic material to the soil combined with wetting and covering of the soil with a plastic tarp to seal out the air. The two practices differ in that ASD sometimes relies more heavily on creating anaerobic conditions in the soil than actual solar soil heating – Browne experimented with almond hulls and shells as well as rice bran as soil amendments for his ASD research. 1 What about tree health? Simmons said that after soil tests showed biosolarization worked well in the Chico orchard – killing the target pests – he has decided to continue gathering data to see how the new trees planted on the soil where biosolarization took place are doing. "We have been monitoring tree health and vigor ever since the trees were established a little over two years ago," he said. "What the data shows for about the first year of growth is that the trees in the biosolarized soils were actually growing slightly slower than the trees in the untreated control soil." Simmons said that while the same changes in the soil that killed the nematodes also required the trees to adapt to the changes, he's now seeing signs of increased growth rates among those trees. "We're starting to see signals that these trees are going to grow faster than those in the control plots, and that's something we'll continue to monitor. Obviously, we hope that the upward trend continues and that all the trees in the biosolarized soils will eclipse those in the controls," he said. "We need to be mindful of the amendment conditions so that we can 1 For more information: https://bit.ly/33AXDf8 The shiny plastic ribbons shown in this bird's-eye view of the UC Davis trial in Crowley's orchard indicate rows that were selected at random and treated pre-plant with biosolarization, while other areas were left untreated as a scientific control. Photo courtesy of Chris Simmons Biosolarization in progress. Continued from page 6