Biological transformation characteristics of N and P in different polytunnel greenhouse vegetable soils

In order to evaluate the soil fertility and quality in different polytunnel greenhouse vegetable soils in Taihu Lake regions from the soil biology point of view, the authors investigated the variation of soil biological indicators, such as urease activity, neutral phosphatase activity, numbers of ammonium oxidizing bacteria and denitrifying bacteria in soils under polytunnel greenhouse cultivation, which is different in vegetable species, different in cultivation history, different in culture systems and different in depth. Results show that the soil urease activity was affected by different vegetable species. The urease activity in polytunnel greenhouse cucumber soil was significantly less than that in polytunnel greenhouse eggplant soil. The soil urease activity and the number of ammonia-oxidizing bacteria tended to increase with the years of cultivation. Some physi-chemical and biological properties in polytunnel greenhouse aggregate were superior to those in polytunnel greenhouse soil. The urease activity and the number of ammonia-oxidizing bacteria decreased slowly with the increase in soil depth in polytunnel greenhouse vegetable soils. The neutral phosphatase activity increased at first, and then decreased with the increase in soil depth. Some physi-chemical properties run down in polytunnel greenhouse soils, and the urease activity and the number of ammonia-oxidizing bacteria were relatively higher when compared with open field soil. These results may provide primary soil biological reasons for the sustainable use of polytunnel greenhouse vegetable soils in Taihu Lake regions