Effects of Agricultural Land-use on Soil Nutrients and the Vertical Distributions in Traditional Cultivated Region,Northern China

The pressures of development and major shifts of land use in agro-ecosystem have increased the need to assess the impact of land use change on soil nutrients.This study was conducted in an area with intensive agricultural land use in Yanqing basin,Beijing Municipality of China to assess effects of land use change on soil organic carbon(SOC),total nitrogen(TN),total phosphorus(TP)and available phosphorus(AP).Soil sample cores to 100 cm depth were collected from orchard land,vegetable land,Maize(Zea mays L.)land and legume(soybean(Glycine max(L.)merr.)and alfalfa(Medicago sativa L.)land in 2005.The results showed that(1)in the whole soil profile(0 ~ 100 cm depth)SOC,TN,TP and AP concentrations were higher in upper layers than lower layers.However,most of the changes occurred within the upper layers of 0 ~ 10 and 10 ~ 25 cm.(2)SOC concentrations are the highest for orchard land and TN,TP and AP concentrations are the highest for vegetable land within 0 ~ 10 cm layers;and SOC,TN,TP and AP concentrations are the highest for vegetable land within 10 ~ 25 cm layers;AP concentrations are significantly higher for vegetable land than the other land use within 25～ 40 cm layers;and TP concentrations are significantly higher for orchard land than the other land use within 40～ 70 cm layers;There were no significant differences in SOC and TN concentrations among the four land use types through the 40 ~ 100 cm soil profile.(3)orchard land could increase soil nutrient contents and carbon stocks to improve the soil quality,while vegetable land could increase soil nutrient contents and the risk of water eutrophication too.