The Experimental Research On The Influence Of Initial Moisture Content To The Transport Of Nitrate In Red Soil

Extensive use of chemical fertilizer or unreasonable fertilization bring a lot of environmental problems, such as environmental pollution, waste of resources, food security, land dropping etc.. According to the research, chemical fertilizer utilization was not more than 30% in China, and utilization rate of nitrogen in every season was obviously lower than 30%. Residual fertilizers in the soil has not only led to serious pollution to soil and water, but high nitrate was in vegetables and other crops that is absorbed by their root which was a serious threat to human health. Therefore, soil conservation, prevention of soil pollution is particularly important because of its durability. The soil infiltration characteristics and migration, distribution of nitrogen has been done a lot of research by predecessors, however, there has few study on the effects of initial moisture content on N infiltration depth and velocity, so it is necessary to conduct a preliminary study, providing reference for reasonable fertilization.Red soil that universally exists in Hunan territory is used for test due to its better representation. Through indoor simulating experiment, this paper studied water and nitrate (NO₃-N) migration features of five kinds of red soil with five initial moisture content. The experimental data shows:(1) Soil moisture content has an influence on migration of water and its distribution in soil. High soil initial moisture content leads to quick infiltration of the moist peak; The infiltration time of completed the same amount of water is shorter and water moves more deep at the same time when the soil initial moisture content is high; The correlation analysis indicates there is extremely remarkable linear correlation (p ＜0.05) between the moist peak and the square root of infiltration time; This indicated the soil moisture content has the remarkable influence on the soil moisture migration and its distribution.(2) Soil moisture content has an influence on NO₃-N migration. The concentration of NO₃-N is high between 0-30cm soil; below 30cm it is few and more evenly distributed. With the initial moisture content increased nitrate nitrogen lies in more deep soil, but they are less residue. After 50% and 60% of the initial moisture passed from id to 11d, the soil profile residues of NO₃-N were detected little closer to the value of the soil below 50cm. This article shows different initial moisture content was little effect to NO₃-N leaching in the red soil. It predicts NO₃-N are less likely to move and lead to groundwater contamination in red soil.(3) With the increase of initial moisture content, the NO₃-N concentration of the measured value was not consistent with the predicted value, especially when the largest margin of 60% moisture, but the results were good performance between simulated and measured values in the overall.Majority of scholars believe NO₃-N was little absorbed in the soil, mainly in the form of solutes. While the soil is enough moisture nitrate nitrogen is almost certain dissolved in the soil solution, affected by the soil moisture and easily leaching. The study is an important component of the research of solute transport that study on the condition of soil salinity for irrigation and nutrients, enrichment and development, Moreover, the theory and technology of irrigation, have an important theoretical and practical significance of production.