Water And Nitrogen Transport In A Typical Fluvo-aquic Soil Configuration And Environmental Risk Assessment At County Scale

Soil configuration is a heterogeneous physical phenomenon developing in the soil profile scale. It is the different permutation and combination condition of the whole soil profile that is generally caused by natural and human activity. As one of the site conditions of agricultural production, soil configuration has quite a significant impact on soil water movement, nitrogen transport and crop root growth, which determines the the level of farmland soil fertility and the crop yield in large extent.The study that relies on the Chinese Academy of STS topics and National Natural Science Foundation project was built on 118 groups of measured data get in way of some scientific experiments within Feng Qiu agro-ecological experimental station of Chinese academy of sciences and Fengqiu County. Experiments analyzed vertical soil zone soil texture and determined the different distribution of the different soil configurations.Experiments got physical and chemical properties of soil, soil water and nitrogen content and other data, analyzed the spatial and temporal change of soil moisture and nitrogen,used the Hydrus-1D simulation model to process the process of water and nitrogen transport, and calculated the soil water storage and nitrate leaching in different soil configurations with balance equation and estimation models. Experiments analyzed the soil configuration distribution within the scope of the county, made the water and nitrogen transport numerical simulation of different configurations in this area, then assessed their environmental risks that combined with other soil materials and locally grown and characteristics. The conclusions have important significance to the environmental risk assessment of different soil configurations in Feng Qiu County and the North China Plain Meadow Soil District.The main conclusions of this research are as follows:(1) Research based on soil sampling and analysis of Chao soil typical configurations between 0 and 2 meters within Feng Qiu Agricultural Experiment Station, accessed to the vertical distribution of soil texture. The typical configuration in Feng Qiu station has coarse soil texture in the tidal superficial layer, a clay layer appeared in the thickness of60 to 90 centimeters, then transited to the fine texture downward. These configurations were the typical soil of the North China Plain that called "Monte gold soil ".(2) Research based on the long-term observations of soil water and nitrogen withinthe cell for 16 Feng Qiu Ecological Agricultural Experiment Station, got a mass of water and nitrogen data in a complete winter wheat- summer maize rotation period. Vertical soil moisture had a certain variation in the temporal and spatial distribution that affected by irrigation time and soil configurations. In March to April and July to August, there were two peaks of moisture content, and the layer of clay between 60 to 90 centimeters had the strongest water holding capacity, moisture change was relatively stable. And two peaks of nitrogen appeared after fertilization and precipitation. The nitrogen change of surface layer was affected by fertilization, the downward layer became stable, clay layer fixed nitrogen at a high level. Because of its adsorption properties, ammonium nitrogen change was not dramatic, but the tendency was still affected by fertilization.(3) Research used the Hydrus-1D simulation model to process the process of water and nitrogen transport, and calculated the soil water storage and nitrate leaching in the typical soil configurations with balance equation and estimation models. The soil water reserves from 0 to 2 meters kept in 450 to 700 millimeters all year, the trend was steady,water reserves of corn season was greater than the amount of wheat season. The water infiltration at 2 meters was uninterrupted in the year. The soil nitrogen reserves from 0 to2 meters exceeded 50 kg/hm2 all year, which goes up with fertilizing amount, so did the nitrogen leakage. Nitrogen leakage of corn season was greater than the amount of wheat season.(4) Research based on soil particle analysis of a plurality of many sampling points within the range of the counties, with the help of the vertical soil generalized maps and hierarchical images to get the soil configuration distribution within the scope of the county: light loam and loam distribution contributed the largest proportion on the 2meters that added up to more than 50%, the others' sequence of content was sand, clay and sandy loam. The distribution of soil configurations was complicated: the middle-fine-coarse configuration represented the most probability about 32.31%,followed by the first were middle- middle-coarse, middle- middle –fine, middle- middle-middle, fine- fine – fine, every proportion exceeded 10%.(5) Research used the Hydrus-1D simulation model to process the process of water and nitrogen transport, and calculated the soil water storage and nitrate leaching in different soil configurations with balance equation and estimation models. Irrigation(rain)and fertilization enhanced the soil water and nitrogen reserves and downstream movement. It is better to have frequent, small amounts of irrigation to reduce the water and nitrogen leakage under 2 meters, but in the sandy soil configurations, this subduction function had no enough function, environmental risk is very high.