Effects Of Different Double-cropping-rice-based Rotations On Rice Yield And Nutrient Runoff Loss In Paddy Field

In order to explore the effects of different cropping systems on double-cropping rice yield and nutrient loss by runoff,we selected a rotation model with less environmental pollution and increased rice yield,thus providing a guide for rice production.Therefore,in this paper,the three plots of rice-rice-(Chinese)milk vetch(DDZ),rice-rice-rape(DDY),rice-rice-potato(DDM)and two kinds of winter-free paddy field(DDB without water,DDP with water)were studied in field plot experiments.The effects of five treatments on photosynthetic characteristics,nutrient uptake characteristics,yield and economic benefits,and nitrogen and phosphorus nutrient runoff characteristics of double cropping rice.The results and conclusions are as follows:1.Rotation treatments(DDZ,DDM and DDY)can significantly improved rice photosynthetic characteristics and enhanced above-ground accumulation of nitrogen,phosphorus.Rotation treatments can significantly promote the chlorophyll content in rice leaves in the tillering and booting stage.DDZ treatment had the largest increase in net photosynthetic rate in the booting stage of early rice,which was 16.60%and 18.56%higher than DDP and DDB,respectively.In terms of above-ground nutrient accumulation of double cropping rice,the accumulation of nitrogen,phosphorus,and potassium in the shoots of early rice by DDZ was the highest.The accumulation of nitrogen,phosphorus,and potassium in the upper part of the late rice treated with DDM was the highest.2.DDZ,DDM,and DDY treatments can significantly increase rice yield and economic benefits.The DDZ,DDM and DDY treatments mainly affected the yield of rice by increasing plant height,spike length,number of spikes per hole,and number of grains per spike.Compared to DDB and DDP treatments,the increase rate of early rice was2.16%~18.32%;the increase rate of late rice was 0.84%~7.66%;the income of paddy field products increased by 1608 yuan/hm~2~12486 yuan/hm~2 in rotation treatments(DDZ,DDM and DDY).3.The loss of TN runoff about all treatments was 14.60~23.21kg/hm~2.The annual total loss of TN treated by DDZ,DDY and DDM was increased by 58.97%,24.52%and 60.07%,respectively,compared with DDB treatment.The annual total loss of TN treated by DDZ,DDY and DDM was increased by 57.78%,23.59%,and 58.87%,respectively,compared with DDP treatment.The loss of runoff of each treated TP was 0.284~0.538 kg/hm~2.The annual total runoff losses of TP,DDZ,DDY,and DDM were 57.75%,63.38%,and 89.24%higher than those of DDB treatment,respectively,which were 37.00%,41.90%,and 64.53%higher than DDP treatment,respectively.The phosphorus loss in paddy fields was dominated by particulate phosphorus,accounting for 71.19%~73.59%of the total phosphorus loss.In summary,the DDM,DDY,and DDZ rotation patterns can increase rice yield and economic efficiency,but at the same time increase the risk of nitrogen and phosphorus pollution.