Mitigating gaseous nitrogen emissions intensity from a Chinese rice cropping system through an improved management practice aimed to close the yield gap

A major challenge in cereal production is achieving the dual goal of closing yield gaps without further undermining environmental benefits by increasing gaseous nitrogen (N) emissions. To address this challenge, we conducted a two-rotation field experiment with four different management practices in the Taihu Lake region to gain insight into crop yields, N use efficiency (NUE), and the emission fluxes of nitrous oxide (N2O), nitric oxide (NO), and ammonia (NH3) from the rice cropping system. The four practices were a control (CK, local practice with zero N-fertilizer), the current traditional practice (CT, local practice with farmers' N management), an improved practice (IP, which closed the yield gap with a reduced N dose of 25%), and a high-yield practice (HY, which maximized the attainable yield with more nutrient inputs). The HY attained the yield potential that was higher by 40% than current yield from the CT. The IP closed the yield gap, achieving 80% of the yield potential, and increased the NUE by 31% and reduced the N surplus by 57% compared with the CT. The lower N surplus of the IP resulted in a decrease in the N2O and NH3 emissions intensity (the N2O or NH3 emission per unit crop yield) of 40% and 65%, respectively relative to the CT. Low NO emissions concomitant with yield increases incurred the marginal NO emission intensity. Thus, the IP should be a promising strategy to increase yield while simultaneously mitigating the gaseous N emissions intensity. Linear or nonlinear responses of gaseous N emissions (N2O, NO and NH3) by N fertilizer to incremental N surplus suggested that reducing the N surplus by both increasing the crop uptake and optimizing N management should be effective in reducing projected gaseous N emissions.