Orchard recycling improves climate change adaptation and mitigation potential of almond production systems

RESEARCH ARTICLE Orchard recycling improves climate change adaptation and mitigation potential of almond production systems Emad JahanzadID1, Brent A. Holtz2, Cameron A. ZuberID2, David Doll2, Kelsey M. Brewer1, Sean Hogan2, Ame´ lie C. M. Gaudin1* 1 Department of Plant Sciences, University of California, Davis, California, United States of America, 2 University of California Agriculture and Natural Recourses, Davis, California, United States of America * agaudin@ucdavis.edu Abstract There is an urgent need to develop climate smart agroecosystems capable of mitigating cli- mate change and adapting to its effects. In California, high commodity prices and increased frequency of drought have encouraged orchard turnover, providing an opportunity to recycle tree biomass in situ prior to replanting an orchard. Whole orchard recycling (WOR) has potential as a carbon (C) negative cultural practice to build soil C storage, soil health, and orchard productivity. We tested the potential of this practice for long term C sequestration and hypothesized that associated co-benefits to soil health will enhance sustainability and resiliency of almond orchards to water-deficit conditions. We measured soil health metrics and productivity of an almond orchard following grinding and incorporation of woody bio- mass vs. burning of old orchard biomass 9 years after implementation. We also conducted a deficit irrigation trial with control and deficit irrigation (-20%) treatments to quantify shifts in tree water status and resilience. Biomass recycling led to higher yields and substantial

improvement in soil functioning, including nutrient content, aggregation, porosity, and water retention. This practice also sequestered significantly higher levels of C in the topsoil (+5 t ha-1) compared to burning. We measured a 20% increase in irrigation water use efficiency and improved soil and tree water status under stress, suggesting that in situ biomass recy- cling can be considered as a climate smart practice in California irrigated almond systems. Introduction The major global challenge facing agriculture is to increase sustainable food production in a changing climate while simultaneously reducing greenhouse gas emissions. Enhancing soil carbon (C) content of agricultural soils provides enormous potential to help reach these goals as C sequestration mitigates climate change [1,2] but also builds sustainability and resilience by improving plant growth conditions and conservation of natural resources [3,4]. Soil organic C (SOC) is essential for soils to function as living ecosystems that provide and cycle nutrients, protect crops from pests and pathogens, conserve water, and reduce risks of soil erosion, thus PLOS ONE PLOS ONE | https://doi.org/10.1371/journal.pone.0229588 March 27, 2020 1 / 22 a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 OPEN ACCESS Citation: Jahanzad E, Holtz BA, Zuber CA, Doll D, Brewer KM, Hogan S, et al. (2020) Orchard recycling improves climate change adaptation and mitigation potential of almond production systems. PLoS ONE 15(3): e0229588. https://doi.org/ 10.1371/journal.pone.0229588

Editor: Ying Ma, Universidade de Coimbra, PORTUGAL Received: August 16, 2019 Accepted: February 11, 2020 Published: March 27, 2020 Copyright: © 2020 Jahanzad et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the manuscript and Supporting Information files. Funding: ACMG SCB16043 California Department of Food and Agriculture https://www.cdfa.ca.gov/ The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: The authors have declared that no competing interests exist.