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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 Whole Orchard Recycling Pays Off in Higher Yields, Improved Soil Health When the time comes to replant an orchard, what if a material existed that, when incorporated into the soil, could increase yield, improve water use efficiency and reduce stress on new trees for years to come? Better yet, what if this yield-increasing material didn't require purchase because it's readily available on the very land where orchard replant will occur? While it may seem too good to be true, recent research from the University of California (UC), Davis, and the UC Cooperative Extension suggests that this scenario is more fact than fiction thanks to the practice of Whole Orchard Recycling (WOR). WOR involves grinding or chipping entire trees at the end of an orchard's productive lifetime and evenly incorporating the resulting biomass into the topsoil prior to replanting a new orchard. In a study published in the journal PLOS ONE, 1 UC researchers observed a 19% yield increase in almond orchard plots where WOR was used compared to control plots where old trees were burned and their ashes were tilled into the soil prior to planting almond trees. Research funding was provided by the Specialty Crop Block Grant Program from the United States Department of Agriculture (USDA) and California Department of Food and Agriculture (CDFA), as well as the Almond Board of California (ABC). "This is an exciting finding," said Gabriele Ludwig, Ph.D., director of Sustainability and Environmental Affairs for ABC. "This research demonstrates tangible benefits of implementing practices to improve soil health – up to this point, there had been a lot of claims made, but little data showing that such a focus can make a meaningful difference in yields." Equally exciting is the fact that this research demonstrates how practicing WOR, or implementing other strategies to significantly increase the soil organic matter in almond orchards, can contribute to the industry's efforts to succeed in reaching not one but two of its Almond Orchard 2025 Goals: achieving zero waste by putting everything grown to optimal use and increasing water use efficiency by reducing the amount of water it takes to grow a pound of almonds. WOR benefits bring the "wow" factor Researchers began studying the trial plots where WOR and burn treatments took place in 2009 at the UC Kearney Research and Extension Center in Parlier. Although both treatments included returning trees' woody biomass back to the soil, the plots where WOR occurred showed significant positive results – see graph below – when compared in 2017 to the burn treatment plots. The gains realized in the WOR study are considered positive indicators of strong soil health, which is defined as soil's continued capacity to function as a vital living ecosystem that can sustain plant life. Healthy soils help cycle and store nutrients, provide stability and support for plant roots, filter and buffer potential pollutants, and regulate water infiltration and storage. UC Cooperative Extension San Joaquin County farm advisor Brent Holtz, Ph.D., who instigated this project and coauthored the WOR research report, notes that the practice of adding organic material to soil dates back thousands of years, long before scientific research sought to quantify its benefits. "The ancient Sumerians figured out 4,000 years ago that adding plant debris and organic material to the soil helped their fields – they just didn't have million- dollar wood chippers," Holtz quipped. "Our soils in the San Joaquin Valley typically only average 1% organic material, or less, making Whole Orchard Recycling a once-in-25-year opportunity to add organic material to your soil." "To me, what was really impressive was our finding related to water use efficiency," said Amélie Gaudin, Ph.D. Gaudin is an 1 www.journals.plos.org/plosone/article?id=10.1371/journal.pone.0229588 Benefits of Whole Orchard Recycling Soil Carbon Soil Aggregation 58% 19% Yield Soil Nitrogen Organic Matter Water Holding Capacity 19% 17% 42% 32% + + + + + + Continue on page 9