黄土丘陵区地形对坡地土壤养分流失的影响

Effects of Relief on Soil Nutrient Losses in Sloping Fieldsin Hilly Region of Loess Plateau

根据黄土丘陵区坡地径流小区试验，研究了次降雨条件下，坡地地形因素中的坡长及坡度与土壤养分流失的关系和土壤可溶性养分离子随径流液而流失的状况。初步结果表明，坡地土壤有机质及速效氮、磷、钾养分的流失强度与坡长呈指数函数关系（ＮＬ＝ａ１·ｅｘｐ（ｂ１ｘ），ａ１＞０，ｂ１＞０），养分流失强度随坡长的增加呈指数增加趋势；坡地土壤有机质的流失强度与坡度呈指数函数关系（ＮＳ＝ａ２·ｅｘｐ（ｂ２ｘ），ａ２＞０，ｂ２＞０）。径流液中的养分离子流失强度大小顺序为：钙离子＞钾离子＞无机氮（ＮＯ－３－Ｎ＋ＮＨ＋４－Ｎ）。

Relief determinants such as slope length and slope steepness are the main reasons for leading to soil nutrient losses. The relationships between relief determinant and soil nutrient loss have been investigated under the condition of rainfall erosion in the runoff plots established in the sloping field in the hilly region on the Loess Plateau. The losses of nutrient ions in the aqueous runoff have also been tested. Some results obtained from the investigation were presented.The relationships between slope length and the loss intensity of soil organic matter, soil available nitrogen, available phosphorous and available potassium can be expressed by the exponential function (NL=a1exp(b1x), a1>0, b1>0), which means that the loss intensity of soil organic matter and available nutrients increases with the increase of slope length. The relationship between slope steepness and loss intensity of soil organic matter can also be expressed by the exponential function. (NS=a2exp(b2x), a2>0, b2>0). The loss insity of nutrient ions in the aqueous runoff is in the order of calcium greater than potassium greater than inorganic nitrogen.