Adaptation of paddy rice in China to climate change: The effects of shifting sowing date on yield and irrigation water requirement

Warming and increasing extreme climate events are expected to reduce crop yields including rice production in China, threatening the Chinese food security. Shifting sowing date has been considered as a key adaptation strategy to sustain rice production in China. However, the extent to which it can mitigate the adverse climate change impact on yield and whether more irrigation is required remains unclear. Here, by driving ORYZA v3 with four climate models (GCMs), we analyzed the impacts of climate change on China rice yield and net irrigation water requirement (NIR) at 21 sites under a wide range of sowing date. We found that without altering sowing date, weighted average rice yield for all sites will decline 5.1, 7.3 and 15.1% in periods 2011-2040, 2041-2070 and 2071-2100, respectively. Yields losses in temperate zones are linked to increased crop development rates with higher temperatures, but in subtropical regions, the reduction is more related to the damage of heat stress during rice heading or flowering periods. NIR increases notably in all regions (up to 71%) except northeastern China, where the shortened growth duration resulted in less time to consume water. When the optimized sowing date is applied, average yield losses will be effectively compensated. To achieve these, rice-sowing date will be shifted by up to 54 days and on average 17.8-23.4 % more fresh water in future periods are needed to meet the water requirement of rice growth. We also found that, due to increasing the frequency of heat events, farmers in Chinese rice production regions (e.g., Yangtze River Basin) will have narrow sowing windows at the end of this century. This study suggests that adequate irrigation and adjusting sowing dates could mitigate the negative climate impacts on rice production in China.