[Effects of Bt corn straw decomposition on soil enzyme activities and soil fertility]

An incubation test with the straws of Bt corn 34B24 and its non-transgenic isogenic line 34B23, Bt corn Nongda 61, and non-transgenic Nongda 3138 was conducted to study the potential effects of Bt corn straw decomposition on soil enzyme activities and soil fertility. No significant difference in soil protease and acid phosphatase activities was found between treatments 34B24 and 34B23; but on day 75 of incubation, soil dehydrogenase activity was significantly higher in treatment 34B24 than in treatment 34B23. The same was true for soil invertase activity on days 15,45, 60 and 75. Soil urease activity in treatment 34B24 was significantly increased on day 30, but decreased on days 45 and 75. A significant difference in several soil enzyme activities was also observed between the treatments of two Bt corn hybrids and their conventional cultivars at some sampling days. After incubation for 90 days, the contents of soil available P and K were significantly lower in treatment 34B24 than in treatment 34B23. The differences mentioned above resulted from the composition of test corn straws, which may be affected by the Bt gene transformation process. In order to accurately assess the effects of Bt corn straw decomposition on soil ecosystem, a standard classification system of soil enzyme activities should be established for different soil types from different regions.