| According to the analysis data of soil survey in the 1950s and 1980s, we have understood the basic situation of soil fertility. Since then, we did not have the same work. Especially the research of soil fertility and evolution in loess regions is quite weak. It can not satisfied with the requirements of soil fertility and management. So, knowing the changes of soil nrtrient content is very important since 1980s, because the nutrient was changed in the conventional of farming, fertilization and management of natural factors and human factors. The research results would provide evidence for scientific management and effective utilization of soil.The study based on historical data of the second soil survey during 1980s and 2001, and typical soil profile of.2001 In order to know the fertility characteristics on typical profile of main agricultural soil in different years, the soil nutrient condition and its temporal variation for recent 30 years were studied through the situ sampling method and the same determination method as historical period.The result showed that the fertility of cumulic cinnamon soil has improved significantly. Since 1980s, organic matter (OM), total nitrogen (TN) and available phosphorus (AP) contents tended to increase above original agric horizon of cumulic cinnamon soil. The content of available nitrogen (AN) increased in topsoil and plow pan. Total phosphorus (TP) increased in topsoil, plow pan, original agric horizon and original topsoil. The content of OM, TN, TP, AN and AP, respectively increased 52.8%, 40.7%, 44.5%, 56.1% and 204.0% in topsoil. Available potassium (AK) content decreased in profile and the topsoil declined 57.6 mg/kg.The fertility of dark loessial soil has improved in topsoil. Nutrient content tended to decrease in soil profile, but the change was not significantly. Compare with 1980s, the content of OM, TN and TP respectively increased 11.3%, 13.6% and 2.8% in dark loessial soil, but TK content decreased in soil profile.General analysis, the change of fertility was not significantly. The content of OM, TN and AN has increased slightly, but TK and AK contents showed a slight decline. The change was not significantly in different years.The potassium content was decreased not significantly in dark loessial soil and loess soil. The other nutrients were accumulated in cumulic cinnamon topsoil and dark loessial topsoil, but the change was not significantly in loess soil. The accumulation of nutrents were significalt in profile of cumulic cinnamon soilAt present, the OM content was lack in these three main agricultural soils in loess regions of Shaanxi. The contents of phosphorus and potassium were abundant in cumulic cinnamon soil. They were fundamental in secondary level. In dark loessial soil and loess soil, the contents of phosphorus and potassium were in the medium level (the third level). In the topsoil, the contents of OM, TN, TP, AN, TP, AP and AK were at a trend of decrease from south to north in the loess area. Aggregate analysis, the contents of phosphorus and potassium were in the medium level, the content of OM and nitrogen were in lack in the topsoil in the loess regions.To sum up, we should pay more attention to intensify the organic fertilizer and the efforts straw returned to cultivated land in the loess area. In order to improve the overall fertility of soil, OM content should be increased and nitrogen input should be enhanced also phosphorus and potassium should be controlled in the central of Shaanxi plain area; While phosphorus should be applied stably in hilly-gully region of tableland and hilly region. At the same time, the dontent of potassium decreased since these recent 30 years. So, in order to ensure the soil nutrient equilibrium and promote the sustainable development of agriculture, the fertilizer of potassium should be adequately used in these regions.
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