How can old orchards help fight climate change? Whole orchard recycling as a climate smart adaptation and zero waste initiative.

As California looks for solutions to climate change, many are looking towards agriculture to increase the amount of carbon and other greenhouse gas emissions stored in agricultural soils. This stored carbon can also improve the productivity and resilience of agricultural systems. To meet ambitious goals set forth by the Yolo County Board of Supervisors in 2020, the state and Yolo County are looking to sustainable land management strategies that benefit soil health, sequester carbon from the atmosphere, support pollinators, and manage erosion.

Yolo County Climate Action and Adaptation Plan

Yolo County is currently developing a Climate Action and Adaptation Plan (CAAP), a roadmap to meet greenhouse gas emission reduction goals, that will help the county be more resilient to climate impacts such as high temperatures, more frequent wildfires, flooding, and drought. The CAAP is driven by input from the public and stakeholders and will include recommendations to lower emissions, protect natural resources, transition to renewable energy, and support sustainable agricultural practices.

The plan, which is an update to the 2011 Climate Action Plan, will include an expanded section on the roles of farms, ranches, and natural lands as part of the solution to climate change. Yolo County Resource Conservation District is leading the Natural and Working Lands Technical Advisory Committee (TAC) to ensure that the agricultural community is represented and has a voice in the process. Through the Natural and Working Lands TAC, a question that is often asked is “How can agriculture mitigate and adapt to climate change while creating sustainable food systems?” An answer to that question for Yolo County’s orchard systems may be whole orchard recycling.

Agriculture as a Climate Solution

Whole-orchard recycling (WOR) is an emerging practice that helps producers manage leftover biomass after an orchard’s productive lifetime. As an alternative to agricultural burning, whole-orchard recycling is the on-site chipping of trees during orchard removal. Those chips are then incorporated into the topsoil to a depth of at least six inches prior to replanting. Historically, orchard disposal was done by burning old trees in the field or sending the debris to biomass facilities. Burning was an ideal choice for growers as it was low-cost and efficient. However, the cost to obtain air quality burn permits has increased in recent years due to its impact on air quality and hazardous emissions. Additionally, restrictions have decreased the number of permissive burn days and most cogeneration plants have closed or are no longer accepting agricultural waste. Other options for clearing orchards were pushing out and grinding up of old trees. The chips are then taken off site. With this method, stored carbon in the old trees is lost from the orchard site. Whole orchard recycling goes a step further to incorporate the chips back into the soil to deliver nutrients and improve soil quality. By utilizing everything from a previous orchard in planting a new orchard, zero waste is lost in replanting.

Whole orchard recycling can be applied to all orchards including almonds, walnuts, pistachios, olives, and other fruit trees. Research by the University of California Cooperative Extension has identified significant advantages to WOR in almond orchards such as increased soil organic matter, improved water holding capacity, and increased cumulative yields (Jahanzad et al., 2020). The research spanned a decade and found that in the first six harvests, there was an observed 19% cumulative yield increase when WOR plots were compared to burned plots. Also, researchers noted that nine years after WOR, 3 tons of carbon were captured and sequestered per acre. By putting woody biomass back into the ground, growers are extending the carbon that was sequestered in an old orchard while improving the water holding capacity of an orchard.

When a new orchard is installed with WOR, the higher levels of soil organic matter appear to lessen the stress to new trees. Because increased soil organic matter results in increased moisture availability, tree roots in the upper layers of the soil are less likely to experience water stress. In addition to increased organic matter, soil carbon sequestration, and water holding capacity, researchers found that WOR also resulted in increased soil nitrogen and increased soil microbial activity compared to the conventional push and burn orchard removal practice.

Learn more about Whole Orchard Recycling:

https://orchardrecycling.ucdavis.edu/soil-health

https://orchardrecycling.ucdavis.edu/research

https://www.almonds.com/sites/default/files/2021-03/WOR%20Grower%20Guide_0.pdf