Alexia Cooper is a environmental systems graduate researcher at UC Merced in California. Her current research involves assessing the effects of compost and cover crops in nut orchard systems within the Central Valley of California. She focuses on evaluating soil health responses to these management changes and their impact on tree health and yields. Prior to this, she explored the potential of biosolids to enhance carbon sequestration in irrigated perennial pasturelands in Colorado. Alexia holds a master’s degree in environmental management from Western Colorado University, CO, and a B.S. in Environmental Science from Westminster University, UT.

Session Code: 1C

Track: CREF Research

Session Name: Compost Impact on Crops and Soil

Session Time: Wednesday, February 7, 8:15 – 9:45 AM

Presentation Title: Sustainable Almond Cultivation in California: Assessing the Impact of Integrated Compost and Cover Crop Strategies on Soil Health and Tree Productivity

Presentation Description: The expansion of almond production in California has led to heightened concerns about the environmental impact of conventional agricultural practices on soil health, water quality, and ecosystem sustainability. In response, there is a growing interest in exploring alternative, sustainable management approaches to mitigate these concerns. Our 5-year study, currently in year 3, was conducted in commercial almond orchards and focuses on the dynamics of nitrogen availability, variations in soil carbon (C) content, microbial activity, and the subsequent effects on tree health due to the application of compost and cover crop practices. There was a slight shift in microbial biomass within the first year after implementation, indicating that compost and cover crops foster the soil biology and thereafter nutrient mineralization. We found a significant difference (p < 0.001) in the availability of NH4+ which was increased by 200% after soil health practices, while no significant change in NO3- was observed. The increase in NH4+ was closely linked to the application of compost. While soil C storage changes are still being processed, we also present the current soil C storage of these orchards. The depleted state of orchard soil C storage represents an exciting opportunity to track changes from these practices, both spatially and temporally. Notably, the implementation of the integrated compost and cover crop system was associated with marked improvements in tree health and productivity within the first year. Tree water stress and stomatal 0.001) conductance were significantly (p< 0.05) improved in treatment blocks compared to controls during harvest, with tree stress in controls having a 29% higher stress response to decreased irrigation. In one site with yield data, there was a 5% increase in production. The study emphasizes the multifaceted benefits of compost and cover crops, highlighting their potential to mitigate soil health degradation, reduce nutrient leaching, and enhance overall ecosystem functioning.