Effects and potential of water-saving irrigation for rice production in China

Water-saving irrigation (WSI) is a promising management practice for sustainable rice production. Shallow-wet irrigation (SWI), controlled irrigation (CI), intermittent irrigation (II), and rain-gathering irrigation (RGI) are four common WSI regimes used in China. Their water saving, pollutant reducing, and yield increasing effects were analysed based on literature survey from multi-site field studies across China. An index system considering the applicability and effect of different WSI regimes was developed to identify their potential distributions across China. The potential overall effect of WSI practices at the country level was then estimated. Results showed that CI had the highest average water saving rate (WSR) of 35.12% and the highest average pollutant reducing rate (PRR) of 54.97%, followed by RGI, SWI, and II; while CI had the lowest average yield increasing rate (YIR) (0.79%), followed by II (5.40%), SWI (8.12%), and RGI (11.80%). Overall, the larger the WSR, the larger higher PRR; but the yield increasing effect will be diminished when the WSR is increased to a certain extent due to the resulting rice water stress. About 94.19% of the total paddy area in China are suitable for WSI practices and the unsuitable ones are mainly due to soil structure deterioration and low soil fertility. SWI is the most applicable WSI regime, suitable for 90.03% of paddy fields, followed by CI and II (23.33%), and RGI (4.16%). By full implementation of appropriate WSI regimes at the country level, the total WSR, PRR, and YIR are likely to reach 22.06-26.41%, 32.11-39.11%, and 5.39-6.87%, respectively. The application of WSI practices in China has noticeable potential to alleviate water shortage and non-point source pollution while ensuring high yield.