Effect Of Fertilizer Reduction On Rice Yield And Control Effect Of Nitrogen And Phosphorus Pollution In Paddy Field

Rice is the main food crop and paddy is the main way of arable land utilization.Nitrogen and phosphorus pollution caused by excessive application of chemical fertilizer in the production process is one of the main sources of agricultural non-point source pollution.In order to reduce nitrogen and phosphorus pollution and ensure rice yield at the same time,this study adopted a field experiment to reduce 100%（DT₀）,90%(DT₁₀),70%(DT₃₀),50%(DT₅₀),30%(DT₇₀),and conventional fertilization(DT₁₀₀).Six treatments were used to explore the effect of rice yield and nitrogen and phosphorus pollution control in paddy fields,to study the effects of fertilizer reduction on the growth and development process of rice,rice composition factors and rice yield,and to study the effects of fertilizer reduction on the dynamic change characteristics of different forms of nitrogen and phosphorus in paddy surface water and paddy soil,as well as the release rules of different forms of nitrogen and phosphorus.The main research results are as follows:（1）Through the experiment of fertilizer reduction,it was found that all fertilization treatments except DT₀ treatment group promoted plant height,tillering number,growth and development process and leaf SPAD value of rice,and the growth and development dynamics of rice were affected by fertilizer application rate to a certain extent.The plant height and tiller value of rice increased with the increase of fertilizer application,while the SPAD value of rice leaves decreased with the high fertilizer application.The overall growth and development process of rice showed that the higher the fertilizer application rate,the earlier the arrival time of each period.Compared with DT₀ treatment group,the arrival time of each fertilizer treatment group was earlier than DT₀ treatment group,but the difference was not significant.There was no significant difference between the effect of each reduction treatment group and DT₁₀₀ treatment group.The reduction of chemical fertilizer can ensure the effect of various indexes in the growth and development of rice,so it is feasible to reduce the amount of chemical fertilizer in the planting process of rice.（2）The influencing factors of rice yield were in the order of empty shell rate>kernel number per panicle>kernel weight per panicle>1000-kernel weight per panicle>ear length per panicle.When there was no significant difference in component factors among rice treatments,the treatment group with less fertilizer application should be preferred.Through the chemical fertilizer reduction test,it was found that the empty shell rate of DT₇₀ treatment group was 6.89%,2.69%lower than that of DT₁₀₀ treatment group（9.58%）,and 1.82%higher than that of DT₀ treatment group（5.07%）,but the difference was not significant.There was no difference in the number of grains per ear among DT₅₀,DT₇₀ and DT₁₀₀ treatment groups,and the grain weight per ear increased with the increase of fertilizer application rate,but the difference was not significant.Compared with DT0 treatment group,the rice yield of each treatment group was increased by 17.46%,15.88%,17.66%,18.55%and 9.37%,respectively.The DT₇₀treatment group had the highest rice yield（685.45 kg per mu）,followed by DT₅₀treatment group（680.31 kg）,DT₀ treatment group had the lowest rice yield（578.13 kg）,and the rice yield of each treatment group ranged from 578.13 to 685.45 kg.The application of chemical fertilizer can promote the rice yield and the indexes of rice yield components,but with the increase of fertilizer application,the growth and development of rice will be inhibited and the yield will decrease.Therefore,in summary,reducing the amount of chemical fertilizer by 30-90%can not only ensure the constituent factor index of rice,but also ensure the rice yield within the average range of the national rice yield per mu.（3）Through the experiment of fertilizer reduction,it was found that the increase of nitrogen and phosphorus concentration in the surface water of the paddy field was significantly related to the amount of fertilizer applied.The higher the amount of fertilizer applied,the higher the content of nitrogen and phosphorus in the surface water.Compared with DT₁₀₀ treatment group,the total nitrogen content of each treatment group was reduced by 69.08%,61.64%,52.97%,42.88%and 22.31%after fertilization.After fertilization,the total phosphorus content decreased by 87.05%,76.72%,68.10%,59.26%and 26.35%.Through the study of soil nitrogen and phosphorus release law of paddy field,the results show that the selection of suitable fertilizer amount is the key to control the process of rice planting.The selection of fertilizer amount to control agricultural non-point source pollution should take both economic benefits and environmental safety into consideration,and take the macro-application threshold as the limit.In conclusion,selecting the appropriate fertilizer application rate can not only reduce the risk of nitrogen and phosphorus loss,fundamentally control nitrogen and phosphorus pollution,but also guarantee the rice yield.