Abstract: The transgenic Bt corn Mon810 and its parental nontransgenic corn (the control) were grown in field to study the quantitative changes of culturable
microorganisms and the diversity of bacterial functional groups in their rhizosphere at different growth stages. There was no significant difference in the colonyforming of cultivable fungi in the rhizosphere of Bt corn and the control across the whole growth period, but significant differences were detected for bact
eria at silking stage and actinomycetes at seeding stage. The diversity of the same bacterial functional groups in the rhizosphere of Bt corn and the control was similar, but the diversity of different bacterial functional groups varied. The number of aerobic nitrogen-fixing bacteria in the rhizosphere of Bt corn was
significantly different from that of the control at five growth stages of the whole growth period, while the numbers of ammonifying bacteria, potassiumsolubil
izing bacteria, and nitrosation bacteria were only significantly different at milking stage, trumpet stage and jointing stage, and tasselling stage, respectively. The numbers of aerobic cellulosedecomposing bacteria and nitrobacteria were significantly different at seedling stage, jointing stage, and trumpet stage, and that of phosphorusdecomposing bacteria was significantly different at milking stage and full- ripe stage. Across the whole growth period except at silking stage and fullripe stage, the population characteristic parameters of the microorganisms in Bt corn rhizosphere were higher than those in nonBt corn rhizosphere.

Key words: Crop yield, Model, Yijinhuoluo County, Conversion of cropland into forest and grassland areas