Study On The Cycle And Migration Of Nitrogen And Phosphorus In Rice Duck Complex System

Farmland non-point source pollution has become an outstanding environmental problem in recent years in China,and the loss of nitrogen and phosphorus in paddy fields has become the main reason.The integrated rice-growing pattern can reduce the input of nitrogen and phosphorus from the source and increase the nutrient utilization rate of the paddy field system.Based on the full-scale return of astragalus sinicus to the field,this paper designed a multi-species participation model of rice-duck hybrid breeding,by comparing with conventional rice,the comparison between the treatments of duckweed and treatments of non-duckweed,starting from the input and output pathways of nitrogen and phosphorus in the rice-duck compound system,analyzed the migration and circulation characteristics of nitrogen and phosphorus in the system,and the effects of duckweed on the migration and circulation of nitrogen and phosphorus were also analyzed.The main research results are as follows :(1)Compared with the treatment of CK(conventional rice cultivation),rice-duck composite breeding mode can increase yield,and is the highest in rice-duck-fish-duckweed treatment(F),with an average yield increase of 9.80%(4.96% to 18.11%),mainly by increasing the number of effective panicles per unit area(6.21% to 28.57%),the total number of grains(8.79% to 26.36%)and the seed setting rate(0.51% to 4.79%),of which the total number of grains showed a significant increase.However,the 1000-grain weight of rice-duck composite breeding mode showed a downward trend.(2)The nitrogen and phosphorus input paths of all treatments were the same,mainly from the return of astragalus sinicus,irrigation and rainfall.Among them,the average proportion of nitrogen in the returned fields of astragalus sinicus was 71.52% to 72.76%,and the average phosphorus ratio was 65.13% to 66.98%.On the output,rice absorption takes up the main part,and the total nitrogen and phosphorus amounts to more than 95%.Compared with the soil bottom value,the TN and TP content of soil increased by 19.83%,15.26%,the content of AN increased by 1.31%,and the content of OP decreased by 14.17%.Compared with conventional rice crops(CK),the TN and TP uptake by rice increased by 0.78% to 29.75% and 22.28% to 53.89%,respectively,and the loss of nitrogen and phosphorus was reduced overall.(3)The content of TN and TP was increased in the treatments of duckweed and treatments of non-duckweed.The TN content of soil,TN uptake by rice,and TN output of aquatic products increased by 2.19%,13.62%,and 13.02% respectively.,the TP content of soil,TP uptake of rice and TP output of aquatic products increased by 18.03%,16.89% and 9.29% respectively on average,indicating that the utilization rate of nitrogen and phosphorus was increased by raising ping.