Location: Water Management ResearchTitle: Influence of whole orchard recycling on greenhouse gas emissions and soil health in a new almond orchard
|CULUMBER, MAE - University Of California - Cooperative Extension Service|
|HOLTZ, BRENT - University Of California - Cooperative Extension Service|
|GAUDIN, AMELIE - University Of California, Davis|
|JAHANZAD, EMAD - California Department Of Food And Agriculture|
|MARVINNEY, ELIAS - University Of California, Davis|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/15/2020
Publication Date: 8/10/2020
Citation: Culumber, M., Gao, S., Poret-Peterson, A.T., Holtz, B.A., Gaudin, A., Jahanzad, E., Marvinney, E. 2020. Influence of whole orchard recycling on greenhouse gas emissions and soil health in a new almond orchard. American Society of Horticultural Science Annual Conference (Virtual), August 10-13, 2020. p. 32896.
Technical Abstract: Whole orchard recycling (WOR) incorporates orchard waste on-site, without burning or moving debris to another location. When mulched into the soil, high carbon (C) containing amendments like woodchips increase soil organic matter (SOM). Agricultural research has found both decreases and increases in carbon dioxide (CO2) and nitrous oxide (N2O) greenhouse gas (GHG) emissions depending on the quality and quantity of amendments, fertilization rates and types, and soil biological and chemical characteristics. A study was initiated fall 2017, on a 35-acre orchard in Parlier, California to investigate the impact of a high rate of recycled woodchips (85 tons/acre dry weight) on surface N2O and CO2 emissions, soil factors, and tree establishment. Four replicated 0.5-acre plots were established for treatments with or without (control) wood chip mulch incorporated into the top 12 inches of soil. Woodchip treatments had higher N2O and CO2 emissions compared to controls in the fertigated drip line in the first two years after orchard recycling. Compared to the control, higher N2O fluxes in the woodchip treatment resulted during the first four days after fertigation; other times they were consistently similar. Total N2O emissions were estimated to be 0.7% and 1.1% of N applied from the control and woodchips, respectively during the first year, and reduced to 0.3% and 0.6% during the second year. Woodchip mineralization is one of the major sources for CO2 emissions. Emission data suggests mineralization rates were highest during the first year and decreased with time. Data collection and analysis of the impacts of WOR and orchard management on cumulative GHG emissions is ongoing. Soil organic matter and total N levels declined in the first two years after replanting, although increases are expected in consecutive years as was observed in a previous long-term study of WOR impacts on soil conditions. Due to the large imbalance of carbon to nitrogen following WOR, orchard N fertility applications were 2.4 times larger (68 lbs N /acre) than the standard recommendation for newly planted almond orchards in the first year, however satisfactory tree growth and nutrition levels rates resulted in half the guideline rate application (30 lbs N/acre) in the second year. Tree size was no different between conventionally managed and woodchipped plots by the end of 2019. Further research is needed to pinpoint the optimal timing and necessary season long fertility rates in the first growing season after recycling to reduce N2O emission losses in the first season.