Effects Of Different Water And Fertilizer Regulation Schemes On Water Use,Rice Growth And Pollutant Emission Of Rice Planting Areas In Southern China

The study of pollutant emission change rule of paddy field under different water and fertilizer management modes has become a hot issue in this discipline.The rice growing area in south China was taken as the research object in this paper.With different water and fertilizer regulation schemes as the research carrier,the combination of field experiment,indoor analysis and mathematical model were used as research methods.Under the regulation of different types of water and fertilizer in different regions?plain area,coastal plain area and hilly area?,this paper were studied rice water demand regular,water use efficiency,rice population growth index change regular?including tillering,leaf area index,plant height,root activity,dry matter accumulation?,total nitrogen?TN?,total phosphorus?TP?,ammonium nitrogen?NH₄⁺-N?and nitrate nitrogen?NO₃^--N?emission regular?including surface water runoff and groundwater leakage in rice field?.In addition,the entropy weight TOPSIS multi-objective decision-making model was used to optimize different water and fertilizer regulation schemes,so as to provide some scientific basis for optimizing reasonable water and fertilizer regulation schemes.The main conclusions are as follows:1.Rice water demand mainly reflects the biological characteristics of plants and different varieties,which is affected by climate,soil and other factors,but rarely affected by water and fertilizer treatment.By effectively controlling the field water layer,the water-saving irrigation model can not only ensure the physiological and ecological water needs of rice,but also reduce water evaporation and significantly reduce the water consumption of rice fields.Compared with traditional water-saving irrigation mode,modified water-saving irrigation that increases the upper limit of rain storage in plain area mode requires a large amount of water because it takes a long time to build water layer in the field during the growth period.Compared with improved water-saving irrigation in hilly areas mode and traditional water-saving irrigation mode,the difference in water demand is not significant.Different fertilization methods had no significant effect on rice water demand.2.Compared with conventional irrigation mode,"water-saving irrigation mode+three times of fertilization"can significantly improve yield and water utilization.The experimental study shows that the water-saving irrigation model can play an important role in increasing production,and some of the experimental stations have reached a significant level.Compared with different fertilization methods,the yield of three times was the best.The water productivity of irrigation in two times fertilization treatments was significantly lower than that in other treatments,and the water productivity of irrigation in three times fertilization treatments is best.The productivity of irrigation water is affected by both yield and irrigation water,which is the accumulation of the two effects.3."Water-saving irrigation mode+three times fertilization"has certain promoting effect on physiological growth of rice.The water-saving irrigation mode is beneficial to the rational distribution of tillering and earing,leaf area and the maintenance of root activity in the later growth stage of rice.At the same time,it had a balance effect on rice dry matter accumulation,but had little effect on rice plant growth.The influence of modified water-saving irrigation that increases the upper limit of rain storage mode and traditional water-saving irrigation mode was significantly different on rice growth characteristics.Compared with different fertilization methods,under three times fertilization treatments rice tillers,roots and dry matter accumulation showed the best performance.4.Rice paddies non-point source pollution mainly comes from the surface drainage and underground leakage out of the nitrogen,phosphorus and other substances.Among them,surface drainage is the main source of paddy field pollution,which accounts for23-90%of NH₄⁺-N,NO₃^--N,TN,TP and COD.Compared with conventional irrigation,"water-saving irrigation mode+three times of fertilization"can effectively reduce the discharge of groundwater and surface water pollutants in rice fields.Among them,the emission reduction effect of improved water-saving irrigation that increases the upper limit of rain storage mode is better than that of traditional water-saving irrigation mode.Compared with different fertilization methods,two times fertilization methods produced the largest amount of pollutants,and three times fertilization methods had the best effect.5.TOPSIS multi-objective decision-making model with entropy weight was used to establelish the irrigation and drainage evaluation index system based on the unity of resources,ecology and benefits.According to this,the reasonable regulation scheme of water and fertilizer in plain and hilly area was determined.The results showed that:for plain areas,"W1F3"?traditional water-saving irrigation mode+three times of fertilization?/"W3F3"?improved water-saving irrigation mode by raising the upper limit of rain storage?was most beneficial to the comprehensive benefits of high yield,water saving,pollution reduction and fertilizer conservation.For hilly areas,"W2F3"?improved water-saving irrigation mode+three times of fertilization?is most beneficial to the comprehensive benefits of high yield,water-saving,pollution reduction and fertilizer conservation of rice.