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United States Department of Agriculture

Agricultural Research Service

Research Project: DEVELOP AND IMPROVE STRATEGIES FOR MANAGEMENT OF IRRIGATED AGRICULTURAL CROPS AND SOILS

Location: Northwest Irrigation and Soils Research

Title: Decomposition of Bt and non-Bt corn hybrid residues in the field

Authors
item Tarkalson, David
item Kachman, Stephen - UNIV OF NEBRASKA-LINCOLN
item Knops, Johannes - UNIV OF NEBRASKA-LINCOLN
item Thies, Janice - CORNELL UNIVERSITY
item Wortmann, Charles - UNIV OF NEBRASKA-LINCOLN

Submitted to: Nutrient Cycling in Agroecosystems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 21, 2007
Publication Date: September 11, 2007
Citation: Tarkalson, D.D., Kachman, S.D., Knops, J.M., Thies, J.E., Wortmann, C.S. 2007. Decomposition of Bt and non-Bt corn hybrid residues in the field. Nutrient Cycling in Agroecosystems. 80:211-222.

Interpretive Summary: Results of one laboratory study indicated that six transgenic crops expressing the Cry1Ab insecticidal protein from Bacillus thuringiensis (Bt) decomposed at a slower rate than their respective non-Bt isolines. This study was conducted in West Central Nebraska to determine the decomposition rates and carbon composition of commonly grown Bt and non-Bt corn hybrids in the field. Leaves, cobs, and stalks of the corn hybrids were placed in litterbags, buried in the soil, and recovered 5, 11, 17, and 23 months after placement in the field. The rates of decomposition did not differ between the Bt and non-Bt corn hybrids. Plant parts differed in their rates of decomposition, with leaves > stalks > cobs. There were differences in carbon fractions between Bt and non-Bt residues, but these differences did not result in differences in their rates of decomposition. The results of this study suggest that the Bt and non-Bt corn hybrids used in this study should not cause differences in carbon sequestration when grown under similar conditions.

Technical Abstract: Results of one laboratory study indicated that six transgenic crops expressing the Cry1Ab insecticidal protein from Bacillus thuringiensis (Bt) decomposed at a slower rate than their respective non-Bt isolines. Consequently, litter decomposition rates, nitrogen cycling, and carbon pools may change in agricultural systems as the result of the widespread use of Bt crops. In this study, we assessed the decomposition rates and C composition of commonly grown hybrids of Bt and non-Bt isolines of corn (Zea mays L.) in the field. Leaves, stalks, and cobs from two Bt corn hybrids (Pioneer 34N44Bt and NC+4990Bt) and their non-Bt isolines (Pioneer 34N43 and NC+4880) were analyzed for C fractions (soluble C, lignin, hemicellulose, and cellulose) and total C and N content. Litterbags containing these residues were buried at a depth of 10 cm in a Holdrege silt loam (fine-silty, mixed, mesic Typic Argiustolls) soil and recovered 5, 11, 17, and 23 months after placement in the field. There were no differences in the rates of decomposition between the Bt and non-Bt corn residues. Plant parts differed in decomposition rates where leaves > stalks > cobs. There were differences in C fractions and C:N ratios between Bt and non-Bt corn residues, and between companies (NC+ and Pioneer), however, these differences did not result in differences in their rates of decomposition. For each plant part, there were no differences in lignin content between the Bt and non-Bt residues. These data suggest that the Bt and non-Bt corn hybrids used in this study should not cause differences in carbon sequestration when their residues decompose under similar environmental conditions.

Last Modified: 4/19/2014
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