Change of soil nutrients under greenhouses under long-term fertilization condition

The content of organic matter,nitrogen,phosphorus and potassium in covered soils were increased compared with uncovered soils nearby,the rate of increase was PKNOM, and the contents of available S、Mg、Mn、B、Zn and Cu in covered soils were also increased.There was a tendency that the contents of organic matter and most nutrients were increase with the cultivating years.The contents of available Ca and Fe in covered soils were distinctly decreased compared with uncovered soils nearby,and there was a tendency that the longer the soils were cultivated,the lower the content of available Ca and Fe were.The NO3--N content in the top layer of covered soils and in the groundwater of covered soils increased by 2.10-8.44mg/kg and 5.56-49.25mg/kg compared with uncovered soils nearby,respectively.