连续种植Bt玉米对土壤微生物群落的影响

In this study, two Bt corns (5422Bt1 and 5422CBCL) and their conventional corn 5422 were continuously planted for five times in greenhouse; the buck soil (0-20 cm, 20-40 cm and 40-60 cm) and root surface soil around roots of corn plants were sampled. Microbial community were investigated to elucidate whether the soil microbes were affected after Bt corns were continuously planted for five times, so as to provide a scientific basis for Bt corn planting in field. Our results showed that the number of bacteria, fungi and actinomyces in the buck soil (0-20 cm, 20-40 cm and 40-60 cm) was mainly affected by soil layer, planting frequency and their interaction. In the same soil layer and planting time, there were no significant differences in the number of bacteria and actinomyces after continuous planting of Bt corns for five times. But the number of fungi in 20-40 cm bulk soil was affected after the first planting of Bt corns, with more fungi in the soil planting Bt corns than their conventional corn. No significant differences were observed in the number of bacteria, fungi and actinomyces in the root surface soil after continuous planting Bt corns and their conventional corn for five times. Planting frequency was the major factor affecting the number of soil microbes (denitrifying bacteria, phosphorus bacteria and potassium bacteria) in the plough layer (0-20 cm). In the same planting time, the planting of 5422Bt1 did not affect the number of denitrifying bacteria, phosphorus bacteria and potassium bacteria in the plough layer. After 5422CBCL was continuously planted for three and four times, the number of phosphorus bacteria was higher; while after 5422CBCL was continuously planted for four times, the number of potassium bacteria was obviously lower, as compared to the planting of 5422. After the fifth planting of Bt corns and conventional corn, no significant differences existed in the number of denitrifying bacteria and phosphorus bacteria in the root surface soil, but the planting of 5422Bt1 resulted in a remarkable decrease in the number of potassium bacteria.