Effects Of Applying Chinese Milk Vetch Under Reduced Fertilizer Application On Soil Structure And Nutrients In Double-season Paddy Fields

Chinese milk vetch is one of the green fertilizers with a long history of planting in southern China,which is rich of nutrients.It can increase and stabilize crop yield,improve soil structure and increase soil fertility.The development of green manure production not only has a traditional role and status,but also has great significance for modern agricultural production.Therefore,carrying out research on green manure and increasing the role of green manure in agricultural applications have an important supporting role in promoting the reduction of chemical fertilizers and efficiency and sustainable agricultural development.In this study,use a double-crop rice experiment for 11 consecutive years,with 6treatments:CK（without fertilizers）,F100（conventional single application of fertilizers）and the Chinese milk vetch application of 15000（GM₁）,22500（GM₂）,30000（GM₃）,37500（GM₄）kg/hm²with the application of 80%fertilizer.The effects of Chinese milk vetch pressure reduction on the yield and yield stability of double-season rice,the stability of soil structure,the efficient use of nutrients and the effect of soil fertilization under reduced fertilizer application were studied.The feasibility of Chinese milk vetch to replace chemical fertilizer and the suitable amounts of pressure Chinese milk vetch.It provides a theoretical basis for weight loss and efficiency improvement and utilization of Chinese milk vetch in southern double-season rice areas.The main results of the research are as follows:（1）Under the condition of reduced fertilizer application by 20%,Chinese milk vetch increase the yields of early and late rice and the whole year’s rice,and when the pressure of Chinese milk vetch was 30000 kg/hm²,the early and late rice seasons with the highest rice production.Compared with the CK treatment,the rice yields of the early and late rice seasons increased 78.4-90.3%and 42.2-46.5%;compared with the F100 treatment,the reduced application of chemical fertilizers to use Chinese milk vetch15000-37500 kg/hm²,there was no significant difference in rice yield between late rice and early rice throughout the year.Compared with the CK treatment,the treatment of reduced application of chemical fertilizers and the utilize of Chinese milk vetch significantly reduced the coefficient variation of interannual yield and improved the stability index of rice yield.（2）Compared with the CK and F100 treatments,when the application rate of 20%reduction of chemical fertilizer with Chinese milk vetch15000-37500 kg/hm²,the contents of soil organic carbon,available phosphorus,total nitrogen and alkaline nitrogen were significantly higher than F100 treatment.Considering the soil nutrient stability factors,under the condition of reduced application of chemical fertilizers in this experiment,it is more appropriate for Chinese milk vetch to utilize about30000 kg/hm².（3）Compared with the CK and F100 treatments,the reduced application of chemical fertilizers with the amount of Chinese milk vetch significantly reduced the compactness of the soil cultivating layer（0-20cm）,and.The increase in soil compactness decreased significantly,with the lowest treatment at 0-10 cm and 10-20 cm soil layers with F80+GM₃and F80+GM₄,respectively.Compared with the CK treatment,the fertilization treatment,especially the reduction of fertilizer application and the treatment of Chinese milk vetch treatment significantly reduced the soil bulk density,and at the same time,significantly increased the water content in the soil.（4）Reduced fertilization and utilizing Chinese milk vetch can promote the formation and stabilization of 1-2 mm and 0.5-1 mm particle size in soil water-stable macroaggregates.Excessive utilizing of Chinese milk vetch is not conducive to the formation and stability of aggregates>2 mm in size.Compared with the CK and F100 treatments,reducing the application of chemical fertilizers to utilizes Chinese milk vetch can increase the content of organic carbon and total nitrogen in each particle level of water-stable macroaggregates,and it is greatest effect of 1-2 mm and 0.5-1mm particle size,and the effect of reducing the application of chemical fertilizer to use Chinese milk vetch 30000 kg/hm²is the most significantly.（5）Compared with the F100 treatment,the long-term reduction of the application of chemical fertilizers and use Chinese milk vetch significantly improved the utilization rate of nitrogen,phosphorus and potassium in the early rice season and the total input of nitrogen,phosphorus and potassium in the late rice season fertilizer utilization rate,the best effect is achieved by applying chemical fertilizer to reduce the utilize of Chinese milk vetch30000 kg/hm².At the same time,the long-term reduction of application of fertilizer to use Chinese milk vetch can promote the absorption and accumulation of nitrogen,phosphorus,and potassium nutrients in rice plants,which increased with the increase of Chinese milk vetch.In the season,the treatment F80+GM₃was the largest,and in the late rice season,the application of Chinese milk vetch amounts was the largest between22500-30000 kg/hm².Considering comprehensively the yield and yield stability of double cropping rice,the stability of soil structure,the efficient use of nutrients and the effect of soil fertility cultivation,under the conditions of this experiment or in the southern double-season rice planting area with similar climatic characteristics of under the condition of applying 20%chemical fertilizer,it is more suitable to turn over the amount of Chinese milk vetch around 30000 kg/hm².