Benefits, management, and adoption of whole orchard recycling in agricultural fields

Authors: CULUMBER, MAE - University Of California - Cooperative Extension Service; HOLTZ, BRENT - University Of California - Cooperative Extension Service; Gao, Suduan; Poret-Peterson, Amisha; ZUBER, CAMERON - University Of California - Cooperative Extension Service; Thao, Touyee; NIEDERHOLZER, FRANZ - University Of California - Cooperative Extension Service; YAGHMOUR, MOHAMMAD - University Of California - Cooperative Extension Service; CAMARENA-ONOFRE, DIANA - University Of California - Cooperative Extension Service; HODSON, AMANDA - University Of California, Davis; Browne, Greg

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/15/2026
Publication Date: N/A
Citation: N/A

Interpretive Summary: Options for orchard and vineyard disposal have become limited in recent years in California due to the regulatory phase-out of agricultural burning and closure of over half of co-generation plants. Whole orchard recycling (WOR), the grinding and incorporation of whole trees into soil during orchard removal has evolved into a method of tree disposal. Incorporating such large amounts (up to 90 tons per acre) of tree biomass into soil can conserve carbon (C) and return nutrients that benefit tree growth but also present a potential risk for nitrogen (N) immobilization that may require additional N fertilizer application for new tree establishment. In responding to the needs, eight trials were initiated between 2008 and 2019 across California’s Central Valley. Field data had been collected to develop management guidelines following WOR, and document its impact on replanted tree health, soil function, and some environmental variables. This paper summarizes the findings with the most updated knowledge on the benefits, management strategies, and future research needs. Results clearly show that WOR increased soil organic carbon (SOC), bioavailable and total N levels, microbial activity and diversity, improved crop yield, enhanced soil water and N retention, and showed a potential to reduce nitrate leaching. An overall increase in structure and enrichment footprints suggests an increased abundance of nematode groups associated with the enhancement of C nutrient cycling and pest regulation. Carbon dioxide emissions that resulted from woodchips decomposition were highest during the first year following WOR but declined substantially thereafter, which supports the findings on SOC increase and soil property improvement. The large-scale adoption of WOR in California’s orchards are also due to the support of several state incentive programs.

Technical Abstract: Whole orchard recycling (WOR) has become a common practice in California (CA) orchards and vineyards due to declining options for agricultural biomass disposal. WOR is the process by which entire orchard trees or vineyard vines are shredded into chips, spread onto the soil surface, and incorporated into the soil before replanting a new crop. This paper summarizes current knowledge on WOR’s impact on soils, crops, and the environment, and further outlines efforts to promote large scale adoption across CA. From 2008 to 2019, field trials were established at eight sites in the Central Valley to determine best management guidelines and to measure changes in soil health, environment, and replanted orchard performance over time. Biomass incorporation ranged from 56 to 191 metric tons ha-1 across all sites. Results clearly show WOR increased soil organic carbon (SOC) and improved crop yield. WOR improved soil water and nitrogen (N) retention, but nitrate leaching was not significantly reduced. Carbon dioxide (CO2) emissions from biomass decomposition were highest in the first year following WOR but declined substantially thereafter, coinciding with soil carbon (C) sequestration and soil property improvement. State incentive programs and outreach/extension efforts have played a significant role in promoting implementation and fostering acceptance of the practice. While the long-term benefits of WOR are clear, further research is needed to optimize water and fertilizer management in replanted systems. The outcomes of this research and the demonstrated success of WOR in CA provide a model for sustainable orchard recycling practices in other regions facing biomass disposal and soil health challenges.