How We Grow

2021 July/Aug How We Grow

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ZERO WASTE What's in the Pile? Almonds and Dairy Team Up to Fund Composting Research For decades, California's two leading agricultural commodities have enjoyed a productive and synergistic relationship. Rather than decomposing in landfills, almond hulls and shells often find a home on Central Valley dairies where they are upcycled as a feed ingredient and bedding material for cows. While the movement of almond coproducts from orchards to dairies is routine, ongoing research suggests that an even stronger relationship may be possible by sending one of dairy's coproducts – manure-based compost – to almond orchards. "We're very excited about the partnership between the almond and dairy communities to better quantify the benefits of applying dairy compost to almond orchards," said Guangwei Huang, associate director of Food Research and Technology at the Almond Board of California (ABC). According to Huang, the research also looks at the feasibility of incorporating almond woody biomass, such as tree prunings, into dairy manure compost. The prospect not only has the potential to return economic and agronomic value to growers, but it may also provide a solution for sustainable disposal of woody biomass in the orchard. Funded in part by ABC, the California Dairy Research Foundation (CDRF) and the California Department of Food and Agriculture's Healthy Soils Initiative, the three-year study aims to measure the impacts on soil health and carbon sequestration (the intentional storage of carbon in the soil) from the use of compost derived from a mixture of dairy manure and almond woody biomass. Preliminary results show promise for almond growers, suggesting potential benefits such as diversification of plant nutrient sources, addition of organic material to the soil and improved water holding capacity in the tree root zone. Finding mutually beneficial solutions Despite the differences in coproduct materials generated on their operations, almond growers and dairy farmers share a similar challenge of finding increasingly higher value and environmentally- friendly uses for their respective coproducts. Whereas hulls and shells benefit from a more developed market thanks to the state's dairy economy, options for dealing with almond woody biomass – especially tree prunings and sticks – are on the decline compared to a decade ago. "Cogeneration plants used to take a significant amount of woody biomass from growers, hullers and shellers," Huang said. "With changes in clean energy generation pricing, that outlet has been drastically curtailed for our growers, hullers and shellers." For growers, Huang notes that open field burning of tree prunings and sticks is a soon-to-be extinct option due to recent changes in air quality regulations. The California Air Resources Board unanimously approved a plan in February 2021 that will phase out nearly all agricultural burning in the San Joaquin Valley by 2025. Meanwhile, milk producers are looking for more options to put manure to work as a natural fertilizer – a practice they have long used to grow forage crops for their cows. "Dairy farmers know firsthand the benefit of using organic dairy manure, including compost, as a fertilizer and soil health builder," said CDRF Director Denise Mullinax. "While many dairies can efficiently and effectively use all of the manure produced on their farms, some have the potential to export surplus manure for use as a compost and organic matter amendment to other farmers, such as almond growers." The proximity of almond orchards to dairy farms, which generate a steady supply of compost source material thanks to the more than 1.5 million dairy cows in the Central Valley, coupled with the annual production of woody biomass from orchard prunings by growers led ABC and CDRF to cooperate on the research. Research focuses on food safety, yield and soil emissions A research team at the University of California, Davis, is nearing completion of its second year of a three-year study 1 to determine the efficacy of using a dairy manure/woody biomass compost as a nutrient rich and organic soil amendment in almond orchards. "The prospect not only has the potential to return economic and agronomic value to our growers, but it may also provide a solution for sustainable disposal of woody biomass in the orchard." – Guangwei Huang 1 "Carbon Sequestration and Soil Health Improvement in Almond Orchards Using Dairy Manure and Woody Biomass Compost," Almond Board of California 2020 Research Update: Researchers Hossein Edalati and Yike Chen take measurement readings of dairy manure and almond woody biomass compost piles. 15

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