Potential of optimizing irrigation and fertilization management for sustainable rice production in China

Abstract

Flood irrigation and excessive nitrogen (N) fertilizers, which are often applied to paddy fields in China, may exacerbate irrigation water shortages, increase production costs, and cause environmental degradation. However, the effects of optimizing irrigation and fertilization management on N loss in paddy fields across China have not been evaluated comprehensively. In this study, we collected the data for synthetic N fertilizer application and irrigation water consumption in the paddy fields of China from 1979 to 2020 and 2004 to 2020, respectively. Synthetic N fertilizer use and irrigation water consumption in China increased by 145% and 54% during these periods, respectively. Based on the N fertilization rate and irrigation regimes, we constructed a N loss model and estimated the synthetic fertilizer-induced N loss from paddy fields. The N loss from paddy fields increased rapidly in 1979–1998, followed by significant fluctuations in 1998–2007, reaching a peak of 1.65 Tg in 2007 and decreasing steadily to 1.03 Tg in 2020. Notably, ammonia (NH3) volatilization was the dominant pathway of total N loss, followed by N runoff, N leaching, and nitrous oxide (N2O) emissions, contributing to 60.15%, 23.69%, 15.04% and 1.12% of the total loss on average, respectively. High N loss rates mainly occurred in the Yangtze river basin and Southeast coastal rice regions. When applying the optimal N management, water-saving irrigation regimes, and a combination of optimal N and water management, the N loss would decrease by 18.15%, 10.36%, and 26.29%, respectively. By the wide application of optimal N and water management, the N fertilizer use, irrigation water consumption, and N loss were likely to decrease by 0.55 Tg yr−1, 1.55 × 109 yuan yr−1, and 0.36 Tg N yr−1, respectively. Consequently, the net economic benefit rates became positive at the national scale, with the cost of N loss and water consumption reductions being 30.14% and 26.41%, respectively. Our study confirms that optimizing N application and irrigation management in paddy fields has noticeable potential to ensure the green agricultural sustainability and food security in China.