Research On Effect Of Rewater To Water And Nitrogen Distribution In Soil With Single Water Storage Pit Irrigation

China is a water-deficient country, with the development of fruit and forestry in hilly area of north China, drought and soil erosion has become increasingly important. Water storage pit irrigation is a new irrigation method which combines water saving-irrigation and soil conservation. Through many years, research has already turned to field from indoor, the studies on water movement have tended to mature and have some achievements on nutrient transport. The rainfall (rewater) is a common situation after irrigation and nitrogenous fertilization, it can bring the redistribution and loss of nitrogen, in this way the ratio of nitrogen utilization will be reduced and soil nitrate in loss nitrogen will bring serious pollution on environment. Therefore, study on the effect of rewater to water and nitrogen transport in soil and loss risk could bring important significance for further development of water storage pit irrigation.Basing on further understand to the water and nitrogen migration principle of water storage pit irrigation, the paper conducted chamber model test aiming at the effect of rewater to water and nitrogen migration in soil under the condition of single water storage pit irrigation. The effect of rewater to water and nitrogen migration in soil under different rewater volume and different rewater time has been studied. The study result indicates that:(1) Under the condition of single water storage pit irrigation, the water infiltration belongs to free infiltration and the water movement mainly is level infiltration. Soil moisture in the single water storage pit decreases gradually as the radial distance increases. It firstly increases and then decreases as the vertical distance increases. The moisture content reaches the highest at the depth of 50cm-70cm.(2) The distribution of soil nitrate nitrogen under the condition of single water storage pit irrigation has the features of that it's concentration inner the wetting volume is smaller. While ammonium nitrogen in the wet range has the features of that higher is in the middle and lower is around. Nitrate nitrogen moves easily with water in soil and the migration style mainly is convection. As NH4+ is positively charged and soil particle is negatively charged, soil particle has strong adsorption to ammonium nitrogen and ammonium nitrogen transports difficultly with water. The migration style mainly is diffusion.(3) Study of indoor model experiment about water infiltration after rewater under different rewater conditions has been conducted. After rewater, moisture content and wet range increase. As the rewater volume increases, the content increases too. After rewater, moisture content decreases as the radial distance increases and It firstly increases and then decreases as the vertical distance increases. The time between irrigation and rewater is longer and rewater volume is bigger, the wetting volume moisture content's change is bigger. There is a logarithmic relationship between wetting front displacement and time. The moisture movement mainly is level movement still after rewater.(4) The distribution law of soil nitrate nitrogen after rewater under different rewater conditions has been conducted. The distribution of oil nitrate nitrogen has the feature that inner density is lower and round density is higher in the wetting volume. After rewater, density of soil nitrate nitrogen is lower near the pit wall. The highest of the nitrate nitrogen density promotes to the distance and the big rewater has a long distance. Leaching of nitrate nitrogen is more obviously after rewater as the time between irrigation and rewater is longer and the volume is bigger.(5) The distribution law of soil ammonium nitrogen after rewater under different rewater conditions has been conducted. When the rewater volume is smaller (1.75L), the distribution of ammonium nitrogen is more uniform. When the rewater volume is bigger (3.5L), ammonium nitrogen of soil in the middle and deep layer (z=40-80cm) firstly increases and then decreases as the radius distance increases after rewater. Ammonium nitrogen of soil in the middle and deep layer is scoured more seriously as the time between irrigation and rewater is longer and the volume is bigger during the rewater process.