Studies On Nitrogen Movement In Loess Layers And Its Mathmatic Analysis And Simulation.

With the increased use of fertilizers,grain output increased significantly. But,in the worldwide,water and underground water table in the content of nitrogen compounds showed an upward trend in the groundwater an water causing serious environmental pollution. Therefore, from the production, ecological and economic benefits, such as fertilizers and irrigation to consider various aspects of science and configuration, to a reasonable fertilizer inputs. Domestic and foreign scholars in the irrigation and fertilization of NO₃^- -N in the soil and the migration of the nitrogen in the soil and groundwater in the migration process into a more extensive study, and achieved significant results. But in irrigation under the conditions of the Loess fertilization of NO₃^- -N migration laws is small. In different irrigation and fertilization of conditions, the indoor use of tracer tests in the study of loess NO₃^- -N and the migration of dynamic change, agricultural areas for the Loess reasonable fertilizer irrigation, improve water and fertilizer use efficiency and prevent groundwater pollution to provide scientific Based on the agricultural ecological environment and water environmentalprotection is of great significance.This article studies the main conclusions are as follows:(1) In different levels of irrigation, soil moisture proprofile in the changes in a gentle, But,with the increase of water soil moisture is increase corresponding. Irrigation is 235.6mm and 254mm, the water potential gradient in soil moisture under downward migration, migration rate makes more moisture in the soil proprofile relative changes in the distribution of uniform. In small scale irrigation conditions, 0 25cm soil gentle changes in the 25cm below the soil moisture decreased significantly. With the depth of soil moisture on the curve regression analysis, correlation significantly.(2) The same amount of water in the soil fertilization different NO₃^- -Ncontent distribution is different, dealing with the high volume of nitrogen NO₃^- -N in the distribution curve in the low volume of nitrogen. Different depths in the soil NO₃^- -N accumulation is different, with the increase in soil depth, different treatment of soil NO₃^- -N of the cumulative difference between the smaller. From the entire section of NO₃^- -N content, clearly show the soil NO₃^- -N nitrogen content increase with the increased volume of the law.NO₃^- -N content is increase with the nitrogen rate increases raise the low level of nitrogen fertilizer, irrigation can form a layer of NO₃^- -N leaching strong role. In the high amount of nitrogen , NO₃^- -N effectively with the accumulation of nitrogen is not increase in volume increases, the extra amount of nitrogen will be shipped with significant moisture moved to the middle and lower classes, NO₃^- -N content with Nitrogen correlation between the number of changes in pairs. Irrigation impact on the NO₃^- -N content significantly, soil NO₃^- -N content is decreased with the increasing volume, the index was significantly related to model.the leaching of the impact of irrigation is very significant, increase in scale irrigation, deep nitrogen leaching loss also increased significantly. Different combinations in different soil depth for the performance of both soil moisture and nitrogen content is inversely proportional.(3) NH 4+ -N in the soil content distribution unlike NO₃^- -N, as the water continued downward migration, on the lower soil proprofile NH 4+ -N content is smaller than the background value. In humid body, the vast majority NH4+-N concentrated in the scope of 0-20cm, outside the 20cm, the NH 4+ -N content of nitrogen is not increasing infiltration and obvious , In the context of its value did not change significantly. This is mainly due to soil particles with negative charge, NH 4+ -N in the soil solution with positive charge, and after contact with soil colloid particles absorb a large number, result at NH 4+ -N in rapid decline, hampered NH+4 -N migration in the lower soil. (4) Water flux of the overall trend is the decrease in depth as the soil gradually increasing.Water flux and the depth of soil moisture as significant linear relationship. the flux migration of NO₃^- -N is reduced with the increasing depth of soil, the migration flux and migration rate of the big irrigation treatment was significantly higher than that of small one. Comprehensive analysis of indoor tracer test results and the preliminary field test, NO₃^- -N migration flux increased with the volume of water.In 78mm, migration flux is the smallest. Therefore, in order to reduce nitrogen leaching losses, loess areas suitable irrigation should be less than 80mm, the amount of nitrogen should not be higher than 400 mg/cm2.(5) Loess nitrogen accumulated in the infiltration of the affecting factors is: irrigation, fertilization, soil depth, infiltration time and so on. DPS data-processing software is infiltration of the impact simulation model on the single factor, more nitrogen accumulated. Through analysis, the single and multiple factors are fitted with multiple non-linear model of relations.By fitting relationship we can see that time is the most important factor.