Managing irrigation water for sustainable rice production in China

Irrigation provides a reliable water supply to sustain agricultural production, yet the persistent depletion of irrigation water is threatening its sustainability. China's water resources are strained by increasing demand from the rapid development of intensive agriculture, with rice cultivation using the most water. Here, a meta-analysis on the rice system in China was conducted using 2753 paired observations to identify the opportunities of optimized water management (two alternate wetting and drying irrigation methods and one limited flooding irrigation method) to reduce both irrigation water usage and greenhouse gas emissions, maintain yield, and increase income. Compared to farmers' continuous flooding irrigation, optimized management decreased irrigation water usage by 40% while increasing water productivity by 34%. Yield losses occurred under severe soil water shortages, but yield increased by 1-6% under mild alternate wetting and drying irrigation (soil water potential >= -15 kPa or soil water table >= -10 cm) compared to continuous flooding irrigation. Optimized irrigation reduced greenhouse gas emissions by 37% through lower methane emissions and less energy consumption from irrigation. Scenario analysis indicated that optimized irrigation reduced both irrigation water use and greenhouse gas emissions and that the economic return could largely offset the risk of yield losses. Policies that support and invest in both water management and high-yielding cultivation practices should be prioritized in order to pursue the benefits of sustainable rice production for China and similar regions. (C) 2019 Elsevier Ltd. All rights reserved.