| Rice is an important food crop for human beings.The increasing of the world population,the shortage of water resources,the global climate change and the environmental pollution are restricting the development of rice production.On the premise of ensuring rice yield,water-saving irrigation is important for food security and efficient utilization of water resources in China.Alternate wetting and drying irrigation is one of the most effective measures for High-yield and Water-saving cultivation of Rice.Most of the current results are based on the studies of the aboveground growth and development,yield formation,nutrient uptake,rice quality and environmental effects of rice.There are few studies on the effects of alternate wetting and drying irrigation on soil properties in paddy fields.In this study,under the condition of pot experiment,indica rice Liangyoupeijiu and Yangdao 6 were used as materials to set up alternate wetting and moderate soil drying(MD,the lowest water potential in soil was kept at-15 kPa),alternate wetting and severe soil drying(SS,the lowest water potential in soil was kept at-30 kPa),and conventional irrigation(SW,keeping shallow water level)was used as control.The verification experiment was carried out with Yongyou 2640 cultivated in the field.The characteristics of root morphology and physiology,soil properties and their relationship were investigated.The main results were as follows:1.When compared with the control(SW,keeping shallow water level),the increase of MD yield at tillering stage and panicle differentiation is due to the increase of grain number per panicle.The increase of MD yield at productive phase is due to the increase of seed setting rate and thousand-grain weight.The decrease of SS yield at tillering stage is due to the reduction in the number of panicles.The decrease of SS yield at panicle differentiation is due to the reduction of grain number per panicle.The decrease of SS yield at productive phase is due to the decrease of seed setting rate.MD during whole growth period can improve irrigation water utilization efficiency,increase the number of grains per panicle and seed setting rate,and increase the yield of rice.The yield increase of rice under MD during the whole growth period is the highest in all treatments.2.Compared to SW,MD significantly increased root dry weight,root-shoot ratio,root length,root diameter,root volume,root oxidation activity,root absorption surface area and root active absorption surface area.MD can promote early formation of rice root ventilated tissue.MD can also increase root bleeding sap,free amino acids and soluble sugar content,while SS can decrease root bleeding sap,free amino acids and soluble sugar content.3.MD significantly increased soil porosity,the contents of soil available nutrients,the activities of invertase,urease,acid phosphatase and catalase in paddy soils.The quantities of bacteria,fungi and actinomycete in paddy soil were increased under MD.SS can reduce soil enzyme activity and microbial quantity.4.Correlation analysis showed that there were significant or extremely significant correlations between root-shoot ratio,root diameter,root oxidation ability and soil enzyme activity and microbial quantity.The correlation between soil biological characters and yield shows that the activity of invertase,urease and acid phosphatase in each growth period of rice has a significant or extremely significant correlation with rice yield.Soil microbial activity is strong,which is beneficial to the growth and yield of rice.MD is one of the effective measures to improve soil microbial activity. |
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