Optimizing spikelet fertilizer input in irrigated rice system can reduce nitrous oxide emission while increase grain yield

Abstract

Nitrogen (N) fertilizer provides an essential nutrient for rice production, but it also leads to nitrous oxide (N2O) emissions. We investigated twenty years’ literature and conducted two years of field experiments to assess the effects of N fertilizer application on N2O emissions, N use efficiency (NUE), and rice yield in the middle and lower reaches of the Yangtze River, China. This work described the time series of N2O emissions during the total rice-growing period based on the literature’s dataset; the peak N2O fluxes (about 1800 µg m−2 h−1) were observed at 0.4–0.55 relative days after transplanting (during the mid-season drainage period). Moreover, we established a positive linear correlation between the seasonal N2O emission and N fertilizer input in this study region (R2 =0.36). The literature’s results suggested that 30%–60% total N fertilizer input as spikelet fertilizer helps obtain an approximate 38% NUE and 8.8% grain yield rise in lower N2O emissions. Regarding the field experiments’ results, they confirmed that the rate of basal fertilizer had a significant influence on N2O emissions. The results also found that the yield scaled N2O emissions would decrease with more spikelet fertilizer input. Furthermore, an improvement in N fertilizer utilizes efficiency (agronomic efficiency and partial factor productivity) with the more spikelet fertilizer application while the total N fertilizer would not change. The grain yield in the spikelet fertilizer plots was approximately 20% higher than in the no spikelet fertilizer plots. Altogether, this study indicates that reducing N applied in the earlier growth stages could be an effective and easy-to-follow approach to increase NUE and grain yield while reducing N2O emissions in paddy production.