Soil Nitrogen Accumulation in Different Ages of Vegetable Greenhouses

The accumulation of nitrogen in different utilization age (0, 1, 2, 3, 4, 5, 10, 13-year) vegetable greenhouses soil with multi-point mixed samples was examined in Shenyang suburb, Liaoning province, China. The results showed that the content of N of all samples was increased with the utilization ages of the vegetable greenhouses. For all the samples, the concentration of total nitrogen (TN) and nitrate in the 0-40 cm layer was higher than that in the 40-120 cm. Compared with other samples, the content of TN and nitrate of 13 years of vegetable greenhouse soil is the highest throughout the 0-120 cm. In the 0-20 cm layer, the TN concentrations in 13-year vegetable greenhouse soil is 2 times higher than that in the bare soil, and the concentration of nitrate range from 19.66 mg kg-1 in bare soil to 56.32 mg kg-1 in 13-year vegetable greenhouse soil. These results demonstrated that long-term continuous N input from chemical fertilizers and manure can cause N accumulation in soils and enrich in topsoil.