Long-term compost use and high frequency low concentration fertigation reduce N2O emissions from a California almond orchard

Authors: NICHOLS, PATRICK - University Of California, Davis; SMART, DAVID - University Of California, Davis; ABU-NAJIM, MAJDI - University Of California, Davis; BROWN, PATRICK - University Of California, Davis; HARTER, THOMAS - University Of California, Davis; Steenwerth, Kerri

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2023
Publication Date: 12/7/2023
Citation: Nichols, P.K., Smart, D.R., Abu-Najim, M., Brown, P., Harter, T., Steenwerth, K.L. 2023. Long-term compost use and high frequency low concentration fertigation reduce N2O emissions from a California almond orchard. Soil Science Society of America Journal. 88(2):403-418. https://doi.org/10.1002/saj2.20615.
DOI: https://doi.org/10.1002/saj2.20615

Interpretive Summary: Compost’s use as an agricultural amendment offers an opportunity to reduce organic waste, as mandated in the State of California (USA) (SB 1383). Organic amendments like compost can improve soil physical characteristics and soil carbon content by increasing soil organic matter. We examined the effect of compost application (7-year duration) soil nitrogen retention and emissions of the greenhouse gas, nitrous oxide. Specifically, we measured nitrous oxide emissions after application of fertilizer during irrigation. We observed a 50% reduction in annual cumulative nitrous oxide emissions from fertilizer delivered via irrigation when applied to soil treated with compost. Our findings indicate that long-term applications of compost in perennial crops could reduce losses of the greenhouse gas, nitrous oxide, to the atmosphere.

Technical Abstract: Compost’s use as an agricultural amendment offers an opportunity to reduce organic waste, as mandated in the State of California (USA) (SB 1383). Organic amendments like compost can improve soil physical characteristics and soil carbon content by increasing soil organic matter. We examined the effect of compost application (7-year duration) on soil nitrous oxide (N2O) emissions, inorganic N pools, soil temperature and water content, bulk density, and total C and N content. The orchard (Nonpareil cultivars interplanted with Aldrich and Carmel cultivars, all grafted on ‘Nemaguard’ peach rootstock [Prunus persica (L.) Bratsch]) was on Oakdale sandy loam (Coarse-loamy, mixed, active, thermic Mollic Haploxeralf). Delivering nutrients through the irrigation system, the orchard was fertigated 14 times with urea ammonium nitrate or calcium ammonium nitrate, using high frequency and low concentration (HFLC) fertigation applications (total 195 kg N ha-1). Soil without compost ('no compost') tended to have higher N2O fluxes (up to 2.75-fold) than soil with compost ('compost'). We observed a 50% reduction in annual cumulative N2O emissions from 'compost'. Soil pH, EC, total C and N tended to be greater in 'compost', and bulk density tended to lower in 'compost' than 'no-compost'. No relationships between N2O emissions and soil temperature, volumetric water content, water-filled pore space, and inorganic N pools were observed in either treatment. Our findings indicate that long-term applications of compost in perennial crops, in combination with a HFLC nutrient management program, could reduce losses of N as N2O to the atmosphere.