Research On The Soil Water And Nitrogen Migration And Nitrogen Use In Orchard Of Water Storage Multi-pit Irrigation

Water storage pit irrigation is a new orchard water-saving irrigation method which was proposed to solve the twin problems of water shortages and serious soil erosion in China’s northern hilly and mountainous areas. This method has combined of water-saving and water conservation, reflecting the advantage of a deep three-dimensional irrigation. Common water and fertilizer regulation is a necessary condition for crop growth, due to lack of reasonable irrigation and fertilization measures coupled with the blind pursuit of yield, a large number of fertilizer losses in China’s farmland, nitrogen use efficiency is very low. Studying on the law of water and nitrogen distribution and nitrogen absorption and utilization of plant under the water storage pit irrigation method has the important guiding significance for the development of farmland irrigation and fertilization measures to improve nitrogen use efficiency.In this paper, the law of soil water and nitrogen migration and nitrogen utilization of fruit trees were studied under the impoundment multi-pit infiltration conditions of water storage pit irrigation, and made a comparative analysis of the above-mentioned elements with the common surface irrigation. The main conclusions are as follows:1. Under the water storage of multi-pit infiltration conditions, soil moisture in the vertical increases firstly and then decreases with the deepening of the soil depth, soil moisture was significantly increased in the40-160cm range of soil depth; soil moisture in the radial diminishes with radial distance increase. The concentration of fertilizer solution has less impact on soil moisture.2. Under the impoundment multi-pit infiltration conditions, soil nitrate content in the vertical direction increases firstly and then decreases with the deepening of the soil depth, below bottom of the water storage pit nitrate content increased significantly; soil nitrate content in the radial direction increased gradually with the radial distance increase. Soil ammonium nitrogen content distributed in the vertical direction more evenly and gradually decreased with the increase of the radial distance. With the passage time of the fruit tree phenology, the overall performance of nitrate content has the phenomenon that spread from the storage pit center to around, the overall distribution of ammonium nitrogen is more concentrated and distributed evenly.3. Compared with surface irrigation, soil moisture has the centralization distribution of storage pit in the deep soil under the water storage pit irrigation; under surface irrigation soil moisture is mainly distributed in the surface and deep soil moisture content was significantly less than the water storage pit irrigation.4. Compared with surface irrigation, soil nitrate content of storage pit irrigation was more uniform near the soil surface, the content increased significantly in the100-160cm range of soil depth, the distribution of ammonium content in the vertical was more evenly; under the condition of surface irrigation, nitrate content near the soil surface was significantly greater than the deep. The ammonium nitrogen content on the soil surface was significantly greater than the water storage pit irrigation. At the season of fruit trees growing, nitrate content of water storage pit irrigation distributed more consistently and seasonal variation was small, mainly concentrated in the root zone which will help the roots to absorb nutrients better; nitrate content distribution was more dispersed under the surface irrigation and seasonal difference was large. Compared with the water storage pit irrigation, the ammonium content in the soil surface was larger under the surface irrigation, thus accelerated the volatilization of ammonia.5. Applied15N fertilizer under the water storage pit irrigation in the soil performances centralized distribution in the deep soil near the center of water storage pit, with the passage of phenologies the distribution tended to be stable. Under the surface irrigation15N fertilizer is mainly distributed in the ground and shallow soil layer and is more evenly distributed in the vertical and radial direction.6. Under the water storage pit irrigation, roots of fruit tree vigorous growth, especially the scope of effective absorbent root growth deeper and spread wider than surface irrigation, nitrogen use efficiency of plant organs are higher than surface irrigation. It shows that under the water storage pit irrigation and its fertigation, to some extent, it improved fruit tree’s capacity of nitrogen fertilizer absorption and utilization, this has important practical significance for the planting of fruit trees in the arid regions of northern China.