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Change of Bt protein in soil after growing Bt corns and returning corn straws to soil and its effects on soil nutrients.

ZENG Ping1,2,3, FENG Yuan-jiao1,2,3, ZHANG Wan-chun1,2,3, ZHANG Yan-fei1,2,3, DONG Wen-chao1,2,3, WANG Jian-wu1,2,3   

  1. (1College of Agriculture, South China Agricultural University, Guangzhou 510642, China; 2Ministry of Agriculture Key Laboratory of AgroEnvironments in Tropics, South China Agricultural University, Guangzhou 510642, China; 3Key Laboratory of Agroecology and Rural Environment of Guangdong Regular Higher Education Institutions, South China Agricultural University, Guangzhou 510642, China)
  • Online:2014-07-18 Published:2014-07-18

Abstract: The spatiotemporal dynamics of Bt protein in soil and the change of soil nutrients in rhizosphere soil, root surface soil and soils at 0-20, 20-40 and 40-60 cm were measured in greenhouse experiments. Two Bt corns, 5422Bt1 and 5422CBCL, and their near isogenic nonBt variety 5422 were grown for 90 days and the crop residues were retained to soil. Results showed that 1.59 and 2.78 ng·g-1 Bt protein were detected in the rhizosphere soil with Bt corns 5422Bt1 and 5422CBCL immediately after harvest. However, there were only trace amounts of Bt protein (<0.5 ng·g-1) were detected in root surface soil after 90 days and in bulk soil in the two Bt corn treatments after 30, 60 and 90 days. When corn residues returned to soil, Bt protein declined rapidly within 3 days and only trace amounts of Bt protein were measured after 7 days. There were no significant differences in organic matter, available nutrient (alkaline hydrolytic N, available P, available K) or total nutrient (total N, total P, total K) in root surface soils and soils at 0-20 cm, 20-40 cm and 40-60 cm among the Bt and nonBt corns after 90 days. Sixty days after returning crop residues of 5422Bt1 to soil, the contents of organic matter and total N increased and the content of available K reduced significantly in the 0-20 cm soil depth. There were no significant differences in any other parameter at the 0-20 cm depth, neither for any parameter in the 20-40 cm and 40-60 cm soil depths compared to those in the nonBt corn 5422 treatment. There were no significant differences in soil nutrient contents in Bt corn 5422CBCL treatment compared to those in nonBt corn 5422 treatment except that available phosphorus content was reduced in root surface soils, and total P content increased at the 0-20 cm soil depth after 90 days. When crop residues of Bt corn 5422 CBCL were returned to soil, only available P content in the 0-20 cm soil layer was evidently higher compared to the soil receiving crop residues of nonBt corn 5422. Results suggested that Bt protein released from root and crop residues of Bt corns would not accumulate in soil, and growing Bt corns and returning crop residues to soil would have no significant effect on soil nutrients in general.