Effects Of Alternate Wetting And Drying Irrigation On The Grain Yield And Quality Of Different Drought Resistance Rice

Rice is one of the most important field crops in China, and it accounts for 28% of the total crops planting area. However, rice consumes nearly 65% of total agricultural water consumption and 54% of total national water consumption. Taking feasible irrigation methods to save water consumption and improve water use efficiency in rice production in China is very important for food security and the sustainable development of agriculture.In this study, with twenty one rice cultivars (including 14 japonica and 7 indica rice cultivars) as materials, the effects of different alternate wetting and drying irrigation during whole growth period on grain yield, grain quality, drought resistance and relative morphological and physiological traits were investigated under pot trials. The main results were as follows:1. Alternate wetting and moderate drying irrigation (WMD, re-watered when soil water potential reached-25 kPa at 15-20 cm soil depth) significantly increased grain yield of Yangdao 6 (YD 6, indica) and Hanyou 8 (HY 8, japonica), whereas grain yield of Liangyoupeijiu (LYPJ, indica) and Zhendao 88 (ZD 88, japonica) were declined among twenty one rice cultivars, when compared with conventional irrigation (CI). The indices of drought resistance were much higher in YD 6 and HY 8 than in LYPJ and ZD 88, indicating there were significant differences in drought stress among rice cultivars.2. Significant effects of different alternate wetting and drying irrigation during whole growth period on grain yield and irrigation water use efficiency were observed among rice cultivars with different drought resistance. WMD significantly increased grain yield of YD 6 and HY 8 by 6.9% and 7.5%, whereas grain yield of LYPJ and ZD 88 were decreased by 7.3% and 8.5%, when compared with conventional irrigation (CI). Under alternate wetting and severe drying irrigation (WSD, re-watered when soil water potential reached-50 kPa at 15-20 cm soil depth), the grain yields of these four cultivars all decreased significantly, but the yield decline of LYPJ and ZD 88 were much higher than that of YD 6 and HY 8. WMD and WSD all significantly decreased irrigation water amount and increased the water productivity (grain yield per unit irrigation water, g grain L-1). The water productivity of YD 6 and HY 8 was higher than that of LYPJ and ZD 88 whether under WMD or under WSD.3. WMD significantly increased aboveground dry matter weight, leaf photosynthetic rate, root oxidation activity, cytokinin (zeatin+zeatin riboside) contents in rice roots and leaves at main growth stages, and the activities of sucrose synthase (SuS), adenine diphosphoglucose pyrophosphorylase (AGP), starch synthase (StS) and starch branching enzyme (SBE) in the grains at early and mid-grain filling stage in YD 6 and HY 8, whereas it decreased above indices in LYPJ and ZD 88, and WSD decreased all these indices among four cultivars. The increase in leaf photosynthetic rate, root oxidation activity, cytokinin contents in rice roots and leaves and the activities of SuS, AGP, StS and SBE in the grains after rewetting might be the main physiological reasons for higher drought resistance in YD 6 and HY 8.4. WMD during the whole growing season significantly increased the rates of brown rice, milled rice and head rice of four rice cultivars, and reduced the chalky grains and chalkiness. Eating quality was also improved under WMD. The results were reversed under WSD. The improvement of grain quality was much better in rice cultivars with higher drought resistance than lower drought resistance.