Effect of cultivating years of vegetable field on soil heavy metal content and enzyme activity in plastic shed

In order to discuss effect of different cultivating years on soil heavy metal accumulation and enzyme activity in plastic shed vegetable field and the relationship between them, the 140 samples of soil were collected from plastic shed vegetable field of different cultivating years (0, 5, 10, 15, 20, 25, 30?a), and their heavy metal contents and enzyme activities were determined. The results showed that the contents of Zn, Pb and Cu were most significantly correlated with cultivating years respectively, the contents of Cd, Ni and Mn were significantly correlated with cultivating years respectively，the content of Cr was not correlated with cultivating years. The activities of soil peroxidase, polyphenol oxidase and amylase were most significantly correlated with cultivating years respectively, the activities of soil phosphatase and saccharase were significantly correlated with cultivating years respectively，the activities of soil catalase, urease and protease were not correlated with cultivating years respectively. With cultivating years increasing, the activities of soil polyphenol oxidase and peroxidase were inhibited the contents of Zn and Cu, the sensitivity order was sensitivity of peroxidase to Zn＞sensitivity of polyphenol oxidase to Zn＞sensitivity of peroxidase to Cu＞sensitivity of polyphenol oxidase to Cu. The soil peroxidase and polyphenol oxidase could be regarded as the indicator enzyme of Zn pollution, the soil peroxidase could be regarded as the indicator enzyme of Cu pollution. The study provides a foundation for soil environmental quality evaluation in polluted protected field.