Effect Of Chinese Milk Vetch Returning To Field And In Combined With Rice Straw On Nitrogen Fertilizer Reduction

The important function of the "Rice(Oryza sutiva L.)and Chinese milk vetch(Astragalus sinicus L.)" rotation system is crucial for the fertilizer-saving and efficiency improvement and soil fertility improvement of the paddy field planting system in China.In this study,the "rice and Chinese milk vetch" rotation system was taken as the research object,and several positioning experiments were carried out.Based on rice yield,nutrient accumulation and soil nutrient status,the effects of Mv planting and return on nitrogen fertilizer reduction in rice production,the appropriate volume of Mv under reduced nitrogen,and the effect of Mv planting and return with rice straw on nitrogen fertilizer reduction were evaluated.The main results are as follows:(1)The nitrogen fertilizer substitution effect of planting Mv in a single-season rice system changes year by year,and the nitrogen fertilizer substitution amount ranges from 20% to 40%.Compared with the conventional full-quantity fertilization treatment(100%N),reducing the nitrogen fertilizer by 20% to 40% can ensure rice yield stable or increased.When nitrogen fertilizer was reduced by 20%,the yield increased with the incorporation of Mv,and the effect was the best when the incorporation of Mv was 2500 kg per mu.The effect of increasing rice yield was more obvious when nitrogen fertilizer was reduced by 40%.The yield of rice was the highest when the incorporation of Mv was 2500 kg per mu.(2)Planting Mv can promote the absorption of nutrients while ensuring stable rice yield.Under the condition of reduced nitrogen fertilizer application by 20% to 40%,the accumulation of nitrogen,phosphorus,and potassium nutrients can still be maintained at the original level.Among them,under the condition of reducing nitrogen fertilizer by 40%,the nitrogen and potassium nutrients in rice plants have significantly improved in 2019.When the amount of Mv was 2500 kg per mu,the nutrient absorption of rice under the two nitrogen fertilizer gradients did not decrease.(3)Compared with the conventional fertilization treatment,the treatment of turning Mv can ensure the stability or improvement of soil fertility.When nitrogen fertilizer was reduced by 40% and the pressure of Mv was 2000 kg per mu,the nutrients of rice plants increased significantly.(4)The return of Mv and rice straw(S)to the field is conducive to the stable and increased yield of rice and the maintenance of soil fertility.Under the condition of conventional nitrogen application,the rice yield was significantly increased which treated with Mv and rice straw in the field for two consecutive years;Under the condition of reducing nitrogen fertilizer by 40%,the rice yield treated with Mv and rice straw in the field increased significantly in the second year,and it could ensure that the absorption level of nitrogen,phosphorus and potassium nutrients of rice and soil fertility level would not decrease.To sum up,this study shows that planting Mv can effectively replace part of the chemical nitrogen fertilizer,which is a key means of saving fertilizer and increasing efficiency.The synergistic utilization of Mv and rice straw can stabilize rice yield,promote nutrient absorption and improve soil fertility under the condition of reduced nitrogen fertilizer application,which is an important way to achieve green sustainable development of rice production.