Effects Of Chinese Milk Vetch Incorporation With Chemical Fertilizer Application On Zinc And Iron Concentration And Quality Of Rice

As a type of traditional green manure for paddy field in southern China,Chinese milk vetch can improve soil fertility,promote nutrients in subsequent crops and increase yield.A large number of experiments have been conducted to propose a reduction of nitrogen fertilizer by Chinese milk vetch that can ensure stable and increase crop yield.With the improvement of people’s living standard,they pay more and more attention to the trace elements and quality of rice grain.Rice food is one of the main ways to absorb zinc and iron by human beings,so it is especially important to promote the uptake of zinc and iron in rice and thus improve rice quality.Therefore,this study investigated the effects of incorporating Chinese milk vetch under different levels of nitrogen application,incorporation of Chinese milk vetch and rice straw with60% conventional nitrogen fertilizer and incorporating Chinese milk vetch with zinc fertilizer on rice yield,Zn and Fe uptake and rice quality.The results will provide a theoretical basis for the combined application of Chinese milk vetch and reasonable nitrogen and zinc fertilizer.The main results were as follows:(1)Planting Chinese milk vetch and nitrogen application rate had significant interactive effects on rice yield,grain number per spike,seed setting rate,thousand grain weight,brown rice Zn and Fe accumulation,protein content,and Ca content of milled rice,etc.Planting Chinese milk vetch could significantly improve rice yield by increasing grain number per spike,seed setting rate,and thousand grain weight,promote Zn and Fe accumulations in rice,reduce amylose content,and improve protein content.Under the conditions of Chinese milk vetch planting,compared with no nitrogen fertilizer treatment,40% N fertilizer application and above could significantly increase rice yield and set rate;40% and 80% N fertilizer application could significantly increase rice straw Zn and Fe accumulation,total Zn accumulation,and whole head milled rice rate;60% N fertilizer application could significantly increase brown rice Zn and Fe accumulation by 22.8% and 45.3%,respectively;80%N fertilizer application significantly increased protein content by 14.6%.The results showed that incorporating Chinese milk vetch with 60%-80% N fertilizer can increase rice yield,the absorption and accumulation of Zn and Fe,and the overall improvement of rice quality.Taking factors into account,the treatment of incorporating Chinese milk vetch with 60% N fertilizer is recommended in practice.(2)Under the condition of 60% N fertilizer application,co-incorporating Chinese milk vetch and rice straw was beneficial for increasing rice yield,promoting Zn uptake,and improving rice quality.Compared with the winter fallow treatment,co-incorporation of Chinese milk vetch and rice straw significantly increased rice yield,total Zn accumulation,and protein content by 21.7%,33.3%,and 11.5%,respectively.Compared with the conventional N application treatment,the protein content of rice straw returning alone with 60% N fertilizer treatment was significantly decreased by 44.3%,and there were no significant differences in all indicators between the co-incorporation with 60% N fertilizer treatment and the conventional N fertilizer application treatment.Therefore,the co-incorporation of Chinese milk vetch and rice straw with 60% N fertilizer was more beneficial than the incorporation alone treatment in increasing rice yield,promoting Zn and Fe uptake,and improving rice quality.(3)Planting Chinese milk vetch in winter season was more beneficial for rice Zn uptake than winter fallow.The treatment of planting Chinese milk vetch and applying Zn during the rice season could increase the total accumulation of Zn in rice and available Zn concentration at rice maturity stage.Incorporating Chinese milk vetch was beneficial to increase the soil available Fe content,and the available Fe content was significantly higher before rice transplanting as compared to winter fallow.Therefore,under the conditions of planting Chinese milk vetch,Zn application of 10mg/kg in rice season was more favorable to promote rice Zn and Fe uptake and increase soil available Zn and Fe concentrations.In conclusion,the planting pattern of incorporating Chinese milk vetch with 60%N fertilizer and the co-incorporating Chinese milk vetch and rice straw in the rice season can promote Zn and Fe uptake and improve rice quality while ensuring increased and stable rice yield.Incorporating Chinese milk vetch with basal application of Zn 10mg/kg is beneficial for Zn and Fe absorption and soil available Zn and Fe contents to provide a theoretical basis for Zn and Fe nutrient fortification in rice.