The Nitrogen Dynamics Under The Plastic Mulching In Loess Plateau

In the Loess Plateau crop field is mainly limited to available water and N fertilizer. Plastic mulch as an effective way to improve the soil water content and crop yield in arid areas,has been widely used in the loess plateau region. For the past few years an unreasonable application of plastic film and chemical nitrogen fertilizer polluted to the environment particularly the non-point pollution caused by the farm nitrogen fertilizer loss is becoming a common concerned major issue in developed and developing countries. For this complex giant agricultural ecosystem, the nitrogen in soil and the various dynamic changes and the mechanism of plant is the important basis to reduce the nitrogen loss and sustainable development of agriculture. But there has little study about nitrogen dynamics and mechanism in soil and plant. In this study, we used the semi-arid summer corn field as the experimental material, by the field investigation and field experiment data analysis as the basis, using field experiments to study the effect to plant nitrogen(TN) and soil nitrogen(inorganic nitrogen and total nitrogen) of the management of the film. The results showed that:(1)The soil profile of inorganic nitrogen forms are mainly composed by nitrate nitrogen, soil ammonium nitrogen content is closely related to the mineral composition, so the content is relatively more stabled.(2)The nitrate content in different soil profile with crop growth period and the effect of changes in the way the change, and effect of treatment can significantly increase the content of soil NO3-N in different historical periods. In different soil profile mulching and mulching soil NO3-N content showed similar "N" variations increased with advancing corn growing period.(3)Relative to no mulching treatment, mulching deal nitrogen accumulation of aboveground showing inverted "V" trend. No mulching more nitrogen left to leaves in physiological maturity, that is nitrogen used in vegetative growth more. The mulching treatment can transfer more absorbed nitrogen to the grain for reproductive growth.(4) The nitrogen in soil profiles was showed the "W" variation in all treatments. This "W" phenomenon was delayed with the increase of soil depth. Third leaf to nth leaf stage because the plant root length limit showed the downward trend; Nth leaf stage to blister stage,due to the effect of improved soil hydrothermal condition, in turn, affect the distribution of nitrogen in the soil so is a rise trend. The variation of blister to physiological maturity stage is opposite with the total nitrogen content of the aerial parts of the plant samples. Though the result of the study we can find that mulching have a great influence to soil nitrogen in early corn fertility, the main changes in soil nitrogen fertility is related to the late com growing conditions closely, and mulching can helps to improve the crop yield and nutritional quality of maize, reasonable shrinking farmland nitrogen,organic fertilizer,reasonable use of membrane is an effective measure to reduce pollution of nitrogen loss in agricultural operation management of the nitrogen.