| Purple soil is widely distributed in the Three Gorges Reservoir area, which is an important land resource in the reservoir area. Due to the dense population and steep slope, the soil erosion is serious in this area, which is only next to the loess area in the northwest of China. Because of the purple soil properties, interflow is easily develop in Three Gorges Reservoir area, and moisture and nutrient loss with interflow in purple soil can not be ignored. Research on the Three Gorges Reservoir water and nitrogen transport has important significance for water and soil conservation and water environment protection. Effects of water and nitrate leaching conditions of slope cropland of purple soil in different rainfall intensity, slope, fertilization measures and soil surface properties were studied by using software simulation. The main conclusion as following:In certain rainfall, following the increase of rainfall intensity, all of the rainfall infiltration content, interflow stability time, interflow loss and interflow runoff coefficient in slope cropland of purple soil are decreasing. When the rainfall intensity is 30 mm/h, the interflow stable intensity is about 100 cm3/min, while in other case, this value is up to 180 cm3/min. Because of the double layer soil,water flows out of the soil in the form of preferential flow after the tillage layer is saturated instead of continue infiltrating to non tillage layer, so the purple soil interflow mainly occurs in the tillage layer.There is a significant negative correlation between nitrate nitrogen leaching loss and rainfall intensity. The nitrate nitrogen leaching loss with the interflow account for 4.3%~19.3% of total amount, and it is an important way about the purple soil nitrate leaching. Under the four kinds of rain, dynamic changes of nitrate concentration with time are similar: they are all rapid increase to the peak concentration and then rapid decrease and finally tend to be stable. But there values are different, the greater the rainfall intensity, the faster the rate of nitrate nitrogen concentration increases, the time of reaching the peak value is earlier, and the bigger the peak value is. In addition, the nitrate nitrogen concentration in the non tillage layer is almost 0 during the simulation time, and the nitrate nitrogen loss with interflow on slope cropland of purple soil mainly occurs in the tillage layer.Purple soil water movements are the same in four different fertilization methods. The transport rate of water in the soil represented a decreasing tendency from bottom to the top of the hill. The loss of water in the non tillage layer only occurs after the rain, and it is much lesser than tillage layer. Interflow loss shows as preferential flow, but for a single soil layer, both tillage layer and non tillage layer, it performance as matrix flow. Nitrate nitrogen flow rate, after the rain, was significantly increased. Comparing with the whole layer fertilization, nitrate nitrogen loss with interflow under base fertilization,cross slope banding and slope banding increases of 8.8%, 8.8%, and 19.9% respectively. So the whole layer fertilization is conducive to maintaining the soil nitrate nitrogen.The interflow of purple soil reduces by 34.8%~43.0% when soil surface has formed crust, the interflow stable strength reduces by 42.7%, and the nitrate nitrogen leaching with interflow reduces by 8.6%~34.4%. While under straw mulching, the interflow of purple soil increase by 8.6%~12.6%, the interflow stable strength scaled up 11.1%, and the nitrate nitrogen leaching with interflow increase by 8.6%~15.4%. |
