Effect Of Chinese Milk Vetch And Rice Straw Combining With Reduced Inorganic Fertilizer On Rice Growth And Soil Fertility

Planting Chinese milk vetch(CMV)and returning rice straw(RS)are key factors for improving soil fertility in the paddy field.There are plenty of research studies on the influence of CMV or RS application with different chemical fertilizers(CF)application rates.With the implementation of the banning straw burning policy in China,green manure cultivation under RS returning is becoming common.The C/N ratio of green manure with RS was more effective for microbial growth,which might improve soil fertility,reduce CF and promote rice production.However,the research on the coincorporation of CMV and RS combining with reduced CF is relatively rare.A field trial including three experiments(reduction of CF after planting CMV,reduction of CF after planting CMV and returning RS to the field,and effect of combined application of CMV and RS on soil and plant properties)was conducted to determine the effect of CMV and RS combined with different CF on soil fertility,rice plant growth,nutrient accumulation,and yield.The purpose of this study was to provide a basis for optimizing the application of CF under the condition of planting CMV and RS returning.The main results are as follows:1.The incorporation of CMV with different CF treatments increased rice grain yield compared with the control treatment(CK).The grain yield of the CMV alone treatment(MF0)was 16.9% higher but 7.7% lower than that of the CK and the full amount of CF alone treatment(F100),respectively.Comparing with F100 treatment,replacing 20% CF combined with CMV treatment(MF80)increased rice grain nitrogen(N),phosphorus(P),and potassium(K)accumulation by 36.4%,52.4%,and 27.9%,respectively.Meanwhile,the accumulation of N,P,and K in RS under MF80 treatment was increased by 14.6%,31.0%,and 9.3%,respectively,proving that 20% reduction of CF with the incorporation of CMV could meet the nutrient requirement of rice.2.When the CF level was reduced under the combination of RS and CMV,the contents of soil organic matter(SOM),total nitrogen(TN),and available potassium(AK)in different growth stages of rice were generally higher than those of a single application of CF(F100),and also,the accumulation of N,P,and K in rice were increased.Compared with F100 treatment,the combination of CMV and RS with 80% CF treatment(MSF80)increased the accumulation of rice grain N,P,and K by 27.7%,80.2%,and 22.1%,respectively,and the accumulation of N,P,and K in RS was increased by 36.9%,12.1%,and 14.4%,respectively.3.With 100% CF application rate,the combination of CMV and RS increased SOM,TN,and K content at different growth stages of rice.Compared with F100 treatment,the combination of CMV and RS treatment(MSF100)increased SOM,TN,and AK content at harvesting stage by 8.8%,6.3%,and 21.4%,respectively.The MSF100 treatment significantly increased rice grain and straw yield by 25.8% and 18.1%,respectively,compared with F100 treatment.The effect of CMV and its combination with RS was more obvious in most cases,thus increasing rice N,P,K contents and accumulations.Altogether,our findings suggest that the combination of CMV and RS,as a key mean of saving fertilizer and increasing efficiency,could effectively replace CF by 20-40%.The synergistic utilization of CMV and RS can stabilize rice yield,promote nutrient absorption and improve soil fertility under the condition of reduced CF application,which is an important way to achieve green sustainable development of rice production.