Effect Of Alternative Wetting And Moderate Drying Irrigation During Whole Growth Period On Grain Yield And Soil Properties In Rice

Shortage of water resource is a serious problem in China at present.Rice is one of the most important crops in China,and it is also the largest agricultural water consumer.Continuously increasing rice yield with less water consumption has been one of the main tasks and objectives of grain production in China.Soil properties are the key factors affecting rice yield and constitute the important part in rice production.Alternative wetting and drying irrigation(AWD)is an important water-saving technique widely used in rice production,and there had many reports about the effects of AWD on grain yield,rice plant morphology and physiology.However,little is known about the effects of AWD on soil properties and their relationships with grain yield in rice.With indica rice Liangyoupeijiu and Yangdao 6 as materials and cultivated in pots in this study,the effects of alternative wetting and moderate drying irrigation(WMD,the lowest water potential in soil was kept at-15 kPa)during whole growth period on rice yield,root morphology and physiology,soil properties were investigated.The main results were as follows:1.When compared with the control(SWL,Keeping shallow water level),WMD significantly increased the grain yields of Yangdao 6 and Liangyoupeijiu by 8.8%and 6.0%,respectively.Though total spikelets number under WMD was slightly lower that under SWL,the gains from the increases in filled grain rate and grain weight were higher than the loss of total spikelets number,leading to the increase in grain yield under WMD.The irrigation water were decreased by 20.6%-25.8%,and irrigation water use efficiency were increased by 37.5%-46.0%under WMD,respectively.2.WMD significantly increased root dry weight,root oxidation activity,cytokinin(zeatin + zeatin riboside)contents in rice roots and leaf photosynthetic rate at main growth stages(panicle initiation,heading stage and grain filling stage).These indices were significantly and positively correlated with rice yield.3.WMD significantly increased soil porosity,the contents of soil available nutrients(available nitrogen,available phosphorus,available potassium),the activities of urease,saccharase,acid phosphatase,microbial biomass carbon and nitrogen in soil,and decreased the soil bulk density.The contents of soil available nutrients at main growth stages were significantly and positively correlated with rice yield.The activities of enzymes in soil also had close relationships with soil available nutrients and microbial biomass carbon and nitrogen.WMD improved physical,chemical and biological traits of soil and were helpful to root growth and yield increase in rice.