Effects Of Combined Application Of Organic And Inorganic Fertilizers On Soil Ammonia Volatilization And Nitrate Accumulation In Winter Wheat Field

Excessive application of inorganic fertilizer caused a series of questions, such as the decline of farmland quality, low utilization efficiency of fertilizers and environment pollution. The combined application of organic and inorganic fertilizers could not only overcome the harmful effects that caused by injudicious use of inorganic fertilizer but also solve the pollution that caused by the organic waste, for example the pollution of poultry and animal feces.This experiment was carried out on alluvial soil. We took winter-wheat, a main crop in North China as the experimental materials and set four application rates of pure nitrogen: 100, 200, 300, 400kgN/ha. Under every nitrogen application rate,we set four different combined rates:100%M, 75%M+25%N, 50%M+50%N,100%N. Through the experiment, we intended to find the optimal combination point between wheat yield and the protection of environment through the study of two most important ways of nitrogen losses. The results showed that:The rate of ammonia volatilization was increased with nitrogen application rate. The application of organic fertilizer could decrease the rate of ammonia volatilization and the amount of accumulative ammonia volatilization. After fertilization, the amount of accumulative ammonia volatilization was between 5.354kgN/ha and 8.916kgN/ha, the rate of ammonia volatilization was between 1.824% and 6.119%. The amount of accumulative ammonia volatilization after top-dressing make up to 97% of total ammonia loss by volatilization.The ammonia loss by volatilization in winter-wheat field was mainly caused by top-dressing.The content of nitrate nitrogen in soil increased with nitrogen application rate in different stages of winter wheat. Compared with the single application of inorganic fertilizer, using organic fertilizer could effectively decrease the content of nitrate nitrogen that outside the root zone. Under low fertilization rate, the critical period of nitrate-nitrogen leaching risk in soil was from blooming stage to maturity stage; however, when under high fertilization rate, besides the stage from blooming to maturity, the booting stage to maturity stage was also very critical to the nitrate-nitrogen leaching risk.The application of organic fertilizer could increase total N content in arable layer. The application of inorganic fertilizer under low nitrogen application rate had little effect on total N content, however, when under high nitrogen application rate, the application of inorganic fertilizer could increase total N content. The application of organic fertilizer could increase total P content in arable layer. The single application of inorganic fertilizer could decrease the total P in soil. When the amount of nitrogen fertilizer was equal and as the ratio of organic fertilizer increased, soil organic matter content increased in the same layer of soil. The combined application of organic and inorganic fertilizers could increase the yield of winter wheat effectively.Take a comprehensive consideration among the yield of winter wheat, ammonia loss by volatilization and nitrate-nitrogen accumulation outside of the root zone, we concluded that the best nitrogen application rate is 200kg/ha, provided by organic and inorganic fertilizer, with the proportion of 75% and 25% respectively.