ABSTRACT
The serious soil erosion of the Loess Plateau has deteriorated the soil fertility and soil quality and has changed the Loess Plateau into a low yield district of grain production. We studied soil nutrient loss, soil physical property degeneration, and soil enzyme reduction in a field and laboratory investigation. When fertilizer was not used, and land slope increased from 4 to 16°, the loss of organic matter increased from 108 kg/ha to 2 1 0 kg/ha, total nitrogen from 15 kg/ha to 26 kg/ha, and total phosphorus from 4.41 kg/ha to 13.3 kg/ha. This leads to barrenness, coarseness, and calcification. Because grain size (<0.01 mm) is only 21.5%, equal to half that of 16°, the fraction of soil aggregates is reduced, and there is a drop in amylase as slope increases. On the basis of the above, we made a comprehensive assessment on the environment quality of erosive soil and divided the quality into five grades, i.e., good, fairly good, poor, extremely poor, and deteriorated. This scheme provided a scientific basis for remaking and using the soil resource.
