Site position and tillage treatment effects on nitrous oxide emissions from furrow-irrigated rice on a silt-loam Alfisol in the Mid-south, USA

The development of drought-resistant hybrid rice (Oryza sativa) cultivars has allowed furrow-irrigated rice production systems to become an increasingly popular alternative to traditional flood-irrigation. However, potential environmental implications, such as greenhouse gas emissions, specifically nitrous oxide (N2O), have yet to be evaluated. This study evaluated the effects of site position (i.e., up-, mid-, and down-slope) and tillage treatment [i.e., conventional tillage (CT) and no-tillage (NT)] on N2O fluxes and season-long emissions from a furrow-irrigated rice field on a silt-loam soil (Typic Albaqualfs) in east-central Arkansas. Gas collection from closed-chambers occurred weekly over the 2018 and 2019 rice growing seasons. Nitrous oxide fluxes differed (P < 0.001) among site position-tillage treatment combinations in both growing seasons. In 2018, numeric flux maxima for all site position-tillage treatment combinations occurred at 33 days after planting (DAP). Nitrous oxide emissions in 2018 were greatest (P < 0.1) at the down-slope (3.34 kg N2O ha−1 season−1) compared to both the mid- (2.78 kg N2O ha−1 season−1) and up-slope (2.74 kg N2O ha−1 season−1), which did not differ. For both growing seasons, CT produced greater (P < 0.1) N2O emissions than NT, where mean annual emissions from CT were 3.15 and 2.58 kg N2O ha−1 season−1 for the 2018 and 2019 seasons, respectively. The evaluation of N2O fluxes and emissions from furrow-irrigated rice is essential to understanding the potential environmental impacts of furrow-irrigation as an alternative water management scheme for rice production.