With popularization and application of transgenic Bt (Bacillus thuringiensis) crops all over the world, more attentions were paid to their potential impacts on soil environment. Bt transgenic crops released Bt proteins into soil with straw returning after harvest, plant residues, root exudates or pollen. It had been reported that the released Bt proteins could be absorbed by soil particles and accumulated slowly, which might influence the soil enzyme activities and soil fertility. Bt maize was one of the largest-scale commercialized GM crops, and the potential ecological risks of Bt maize had been widely studied, however , there were still few studies about the influences of transgenic Bt maize on the soil activities under field condition. In a 2-year field experiment, possible effects of transgenic Bt maize on soil enzyme activities were assessed at maize growth stages in 2008 and 2009, and straw decomposition stages after harvest in 2009, respectively. The tested varieties was Bt maize (DK647BTY) and its parental non-transgenci maize (DK647).
Results showed that there were no significant differences in soil urease activity between transgenic Bt maize field and non-transgenic maize field in all growing stages in 2008 and 2009. Soil invertase and acidic phosphatase activities in 2008 and 2009, soil protease activity in 2008 in Bt maize fields were significantly higher than those in the non-transgenic maize fields at bell-mouthed stage and tasseling stage. No significant differences in acidic phosphatase activities were observed between the Bt maize fields and non-transgenic maize fields after the straw returned over all 3 observation of study. The activities of invertase, urease and protease in Bt maize fields were consistently higher than those in non-transgenic maize fields after straw returned. In conclusion, Bt maize tended to improve the the soil enzyme activities at the growth stages and straw decomposition stages, compared to the parental maize. However the effects of Bt maize on the soil enzyme activities were not consistent in the two years, which might be influenced by the climate factors, the extended monitoring are necessary to assess the long-term impact of commercialized Bt maize on enzyme activities in soil ecosystem.