Reducing greenhouse gas emissions in irrigated potato production: Interactive effects of cover crop, bedding timing, and irrigation

Abstract

Bedding, cover crop and irrigation all influence greenhouse gas emissions in cropland soils, particularly nitrous oxide (N₂O) and carbon dioxide (CO₂). In potato production, bedding bundles fertilizer addition, tillage and bed formation. This study evaluated three bedding types - fall, spring and spring following a winter oat cover crop (S + CC) - combined with two irrigation rates (±20% of the AIMM recommended rate) and two N fertilization treatments on growing-season N₂O and CO₂ fluxes, soil N availability and potato yield in Lethbridge, Alberta across 2022–2024. Fall bedding raised soil ammonium and nitrate in the early spring prior to seeding. With intermittent rainfall in 2022, fall-bedded plots showed lower growing-season N₂O fluxes than spring-bedded plots. In 2023 and 2024, however, fall bedding consistently increased N₂O fluxes under more frequently moist conditions (P < 0.05) and S + CC was associated with the lowest sensor-observed soil moisture (diagnostic only; one sensor replicate per treatment) and produced the lowest area-based N₂O emission factors (EFarea) across treatments (P < 0.01). Compared to fall bedding, S + CC reduced the 3-year mean EFarea by 36% and the yield-scaled N₂O intensity (per kg marketable tuber) by 34% in fertilized plots, while preserving yield. N₂O was unaffected by irrigation, likely because rates diverged only in the second half of each growing season and by just ±20% of the recommended rate. Fall bedding caused slightly higher growing-season CO₂ emissions than spring bedding only in 2023 (P = 0.029). Tuber yields showed no significant differences across most treatments (P > 0.05), except for wetter irrigation increasing marketable harvest in 2024 (P = 0.031). These results support spring bedding with a winter oat cover crop as a promising mitigation practice for semi-arid irrigated potato production, achieving substantially lower N₂O EFarea than fall bedding without compromising marketable yield.