| Soil water,soil nutrient loss, soil quality deterioration, eutrophication of rivers and non-point source agricultural pollution problems has seriously affected the survival of the human environmental conditions. Thus, for slope soil moisture, nutrient transport mechanisms and prediction model study of nutrition research and eutrophication of rivers has become the core of research.The position of Zhu Yu river is in the south bank of Weihe shallow Qinling mountains, annual rainfall is 674.3mm, mainly in 7,8,9 months; the basin topography is funnel-shaped closed waters, over the river as the main stream running through them; there are two kinds of farming mode: kiwi and winter wheat- corn rotation; thus, as a relatively independent and representative area for soil nutrient loss risk research Weihe River is an ideal place. Its conclusions to the future conduct of nutrient transfer mechanism and simulation model for loess slope, effective prediction and control of soil nutrient loss, as well as environmental protection and slope water and nutrient management are of great significance.The research objects for simulated rainfall test are nitrate, dissolved phosphorus, total nitrogen and total phosphorus, explores many factors that affect water and nutrient transport mechanisms, to clarify the soil nutrient loss on a variety of factors affect the response characteristics, by comparing different factors which affect soil nutrient losing, providing a scientific basis for non-point source pollution control.Through experimental research, conclusions are as follows:(1)The results showed that soil moisture have a significant impact on sediment runoff in different slope. Unit time and cumulative runoff varies from initial moisture content of 21%> 14%> 7%> 3.5%. This is because the test used high clay content and easy to disperse, while infiltration capacity of the soil is largely controlled by the soil matric potential gradient, so the higher pre-initial water content, the smaller matric potential gradient is, there for the infiltration capacity is relatively low, and thus result in a large runoff intensity. By analyzing the accumulated sediment concentration, found soil accumulated sediment concentration decreases(3.5%> 7%> 14%> 21%) with an increasing moisture content, which mainly affect by the concentration of sediment in runoff, the oncentration of sediment in runoff mainly determined by the characteristics of the soil under the same conditions, the higher soil pre-moisture is,the higher soil cohesion will become in pre-initial rainfall. At a time when runoff is relatively large, and the flow rate is also fast, but sediment in the large amount of soil moisture conditions still smaller than the small initial soil moisture content.(2) The results showed that when soil moisture content smaller than 14%, the difference in moisture content variation runoff solute concentration is not obvious. When the soil pre-moister lagerer than 21%, the concentration of solute to be carried along in the runoff will be significantly increased. This may be due to a low water content and the strong soil infiltration capacity, so some nutrients with the water infiltration into the deep soil. When the water content increases after than 21%, thus infiltration reduced, runoff efficiency increased, so a lot of soluble nutrients from the soil to be exchanged Stripping away. Also found that both the soluble nitrate or phosphorus loss of rainfall rate all follow this variation 3.5% <7% <14% <21%, the higher the initial soil moisture, the faster its topsoil nitrate drain rate nitrogen and soluble phosphorus is. Moreover, when the initial soil moisture ≤14%, although there are different soil nutrient loss rate under different initial moisture, but this difference is not significant, when the soil moisture lager than 21%, soil nutrient loss was significantly increases.(3) For the purposes of power function fitting nitrate concentration changes with the time is better than the exponential function, and for soluble phosphorus, using exponential function fitting is better than a power function. Therefore, for different types of solute runoff, it is recommended using different predictive models, such conclusions are more reliable. According to the above conclusion, it is considered that for Zhu Yu region, using the power function to describe the changes in the concentration of nitrate in runoff and exponential function to describe the changes in the concentration of DP in runoff can get better results.(4) The research shows that the soil moisture has a significant impact on the nutrient concentrations unpolished slope sediment. Soil moisture divided into high water content(≥14%) and low water content(≤7%), it can be considered that when soil moisture content is in the range of high water content, then the whole sediment nitrogen and total phosphorus content decreased with increasing water content; when soil moisture in the low water interval, then total nitrogen and total phosphorus content increases with increasing water content of the sediment. For specific demarcation between the high water content and low water content range of the test interval has not been able to give an accurate line, but this limit must be between 7% to 14%. During the mid rainfall(0-80min), the loss rate of total nitrogen and total phosphorus with rainfall time decreased in the form of power function. Total nitrogen and total phosphorus attrition rate reveals an excellent linear with soil moisture, correlation coefficient R2 of 0.97 and 0.99 respectively. Nutrient loss rates with the relationship between erosion rate showed a linear, which can be used to predict of its nutrient loss rates with soil loss rate.(5) Rainfall intensity and slope has a significant impact on farmland infiltration process. When the slope is fixed, the rainfall intensity has a significant impact on soil infiltration rate, but not a linear. Under the same rainfall intensity, the greater the slope, the smaller soil infiltration rate is.(6) The intensity of rainfall has a significant influence on the runoff of soluble phosphorus, but not linear. Under the same rainfall intensity, runoff of soluble phosphorus concentration in 10 ° is higher than in 5 °. Through study we found that, for Qinling Mountains Zhu Yu region, an exponential function to describe the changes in the concentration of dissolved phosphorus runoff process can get better results. Runoff solute turnover increased with rainfall intensity at the beginning, then decay in accordance with the law of exponential.(7)Rainfall intensity had a significant effect on the total phosphorus content in the sediment, but not linear. Under conditions of 5 °, sediment total phosphorus content should be slightly higher than of 10 °. Sediment total phosphorus loss of rainfall rate decreases with time in the form of power function, sediment total phosphorus loss rate increases with rainfall intensity, Serve an positive correlation, since this experiment only set three kinds of rainfall intensity,, it still cannot tell the exact relationship between the STP loss rate and rainfall intensity. |
PDF Full Text Request