Research On Soil Potassium Loss By Erosion In Loess Area

The Loess Plateau is one of the most serious regions of soil erosion both in China and in the world. The question that soil erosion causes loss of soil nutrient and leads to degradation of land productivity has received many attentions. But the research on soil potassium loss by erosion is under study.In this thesis, with eight events of artificial water-washing test on five different slope gradients, factors affecting soil potassium loss by erosion, such as slope gradient, rain intensity, vegetation coverage, and amount of rainfall are discussed. The results can be used to understand dynamics of soil nutrient transfer in slope land, provide essential for establishing model of soil potassium loss by erosion, recommend rational fertilization application, and increase land productivity. The main results obtained in this study are as follows:(1) When amount of rainfall is 50mm, the amount of slowly available K, rapidly available K, and dissolved K loss are less than 25400kg/km2, 2620 kg/km2, and 1630 kg/km2, respectively.(2) The ranges of ER of rapidly available K, slowly available K, and total K of Huangmian soil (silt loam) are 1.01-1.73, 1.01-1.20, and 1.01-1.05, respectively. The enrichment of rapidly available K is more obvious. K mainly migrated with sediment in unsolvable forms, while slowly available K chiefly removed with soil. The amounts of total K, slowly available K, and rapidly available K loss have positive correlation to amount of soil loss.(3) The amounts of total K, slowly available K, rapidly available K, and dissolved K lost in the runoff increase obviously with the increase of slope gradient. The relationships between slope gradient and amount of total K, slowly available K, rapidly available K, and dissolved K loss can be expressed by exponential functions.(4) The concentration of dissolved K decreases with the prolonging of water-washing time and increases with the increase of slope gradient. But the concentration of dissolved K decreases with the increase of slope gradient, when vegetation coverage 60% and amount of rainfall 100mm.(5) The concentration of dissolved K and amount of dissolved K, rapidly available K, and slowly available K lost in the runoff increase obviously with the increase of rain intensity. Rain intensity has little effect on ER of rapidly available K and slowly available K, and leads some decrease of ER of rapidly available K. ER of rapidly available K increases with the decrease of slope gradient. Rain intensity has more effect on the loss of soil, slowly available K, and rapidly available K than slope gradient.(6) The concentration of dissolved K and amount of dissolved K lost in the runoff increase obviously after fertilizing KCI. The amount of K lost in the runoff obviously increases after fertilizing KCI. KCI mainly loss with the form of dissolved K. ER of rapidly available K almost unchanged after fertilizing KCI, but decreases with the increase of slope gradient.(7) The concentration of dissolved K basically decreases with the increase of vegetation coverage. With the increase of vegetation coverage, the amounts of slowly available K and rapidly available K lost in the runoff obviously decrease. When vegetation coverage is 10%, amount of slowly available K, rapidly available K, and dissolved K lost in the runoff are less 74.51%, 73.84%, and 4.66% than open ground. When vegetation cover-degree is 60%, amount of slowly available K, rapidly available K, and dissolved K lost in the runoff are less 97.49%, 97.31%, and 73.14%. Vegetation coverage (slope gradient 20) has more effect on the loss of soil, slowly available K, and rapidly available K than slope gradient. ER of slowly available K and rapidly available K are some higher than open ground.(8) When rain intensity is 3.33 mm min-1, the concentration of dissolved K of 200mm amount of rainfall is higher than 100mm, except 25. The amount of slowly available K, rapidly available K, and dissolved K increase with the increase of amount of rainfall. Amount of rainfa...