Analysis on soil nutrient characteristics for sustainable land use in Danangou catchment of the Loess Plateau, China

Understanding of the characteristics of soil organic matter (SOM) and soil nutrients at the field and catchment scale is important for refining agricultural management practices and for improving sustainable land use. In order to analyze on SOM and nutrient differences among different land use types and their relationships between land use, landscape position and slope aspect, 94 sampling sites including 7 land uses were selected along 6 transects in the Danangou catchment with an area of 3.5 km(2) on the Loess Plateau of China. Significant differences in SOM, total N (TN), available N (AN) and available P (AP) among these land uses were found.. Higher values in SOM, TN and AN were measured in soils from woodland and grassland, but lower values in the soils from fallow land and cropland. Compare SOM and TN with cropland, intercropping land had high contents. The adjusted R-2 values of regression models for SOM and nutrients with land use, landscape position and slope aspect ranged from 0.501 (SOM) to 0.134 (AP). A comparison between average predicted and measured values for SOM and each soil nutrient revealed that the predicted values in TP and AN for each land use, in SOM and TN except for fallow land and in AP except for intercropping land, shrub land and woodland, fell with in a 95% confidence interval about the measured values. The simplified predicted models of soil nutrients combined with the key value of SOM for soil quality can serve to improve agricultural practices and to provide useful information on sustainable land use. Improvement in SOM and nutrients would be expected from more C inputs including manure and crop residues and alternative cultivation practices such as developing intercropping system, building terrace for soil and water conservation, return the cropland with SOM content less than a key value of 0.44% to the grassland and woodland on the hilly areas similar to the Loess Plateau of China. At the same time, it is recommended that nitrogen fertilization addition could be decreased in the foot slope and increased on the upper slope. (C) 2003 Elsevier Science B.V. All rights reserved.