Laboratory Research Of Influence Of Black Soil Nutrients Loss From Slope

Northeastern black earth region is an important commodity grain base, which is mainly distributed in China’s Songliao basin and Sanjiang plain, it is one of the world’s three major black soil zones. Soil texture of the black earth is loose, and it is rich in organic matter content. Due to natural factors and people’s irrational production and business activities, black earth region had a serious soil erosion, particularly the loss of soil nutrients which caused by the soil erosion is severely increased soil degradation, declining soil fertility. It makes a serious impact on the land productivity, food production and regional socio-economic development of black soil region. Therefore, in order to reveal the mechanism of the loss of black soil nutrient and provide a theoretical basis for forecasting and controlling the loss of black soil nutrient, in this paper, we take black earth as test soil, using artificial simulation of rainfall, studying the effect of slope on the loss of black soil nutrient, like organic matter, total nitrogen, total phosphorus, ammonium, nitrate and available phosphorus. The main findings are as follows:(1)Throughout the precipitation process,under the same slope gradient, content of total nitrogen, total phosphorus, organic matter and other essential nutrients in sediment are showing a fluctuant downward trend with the change of precipitation. And with the increasing slope, a variety of nutrient content in sediment showed a decreased trend.(2) In any slope gradient conditions, with the change of runoff duration, the loss of total nitrogen, total phosphorus, organic matter and other nutrients in sediment show a rising trend, and the relationship between the loss of nutrient and runoff duration can be expressed by an exponential function. And, in addition to ammonium and nitrate nitrogen, the loss of nutrient contents in sediment and erosion of sediment are presented a different degree of correlation. With the increasing slope, the loss of nutrients in sediment shows an upward trend: 9 °> 7 °> 5 °> 3 °> 1 °. When the slope gradient rises to 7 ° and above, a variety of loss of nutrient contents are showing substantial increases. But the mechanical composition and loss of nutrient contents in sediment not have a significant correlation.(3) In addition to the slope gradient of 7 °, at the same slope gradient, total nitrogen and total phosphorus content not produce significant changes with rainfall duration. With the change of slope gradient, total nitrogen and total phosphorus content generate fluctuations, and they reach the maximum value at the slope gradient of 5 °.(4) Throughout the precipitation process,under the same slope gradient, the loss of total nitrogen and total phosphorus in runoff all shows a growing trend in different magnitudes with the change of precipitation, and the relationship between them can be expressed by an exponential function. Under different conditions of slope gradient, the runoff and the loss of total nitrogen have a higher correlation, they are significantly correlated, but the runoff and loss of total phosphorus are less relevant. When the slope gradient of 3 °, runoff and the loss of total nitrogen, total phosphorus have a consistent trend.(5) Throughout the precipitation process, the changes of loss of nutrients in sediment are as follows: matter> total nitrogen> total phosphorus > available phosphorus > ammonium> nitrate. The changes of loss of nutrients in runoff are: total nitrogen> total phosphorus. Under different conditions of slope gradient, the loss of nutrients in sediment shows a growing trend. And when the slope gradient rises from 5 ° to 7 °, the total loss of nutrients in sediment erosion shows a significant growth. The total loss of total nitrogen in runoff shows a wave-type change, with slope gradient changes, the loss of total phosphorus shows a growing trend at the beginning and a decreased trend then.