Decomposition of Bt and Non-Bt Corn Hybrid Residues in the Field |
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Authors: | David D Tarkalson Stephen D Kachman Johannes M N Knops Janice E Thies Charles S Wortmann |
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Affiliation: | (1) United States Department of Agriculture, Agricultural Research Service, Northwest Irrigation and Soils Research Laboratory, 3793 North 3600 East, 83341 Kimberly, ID, USA;(2) Department of Statistics, University of Nebraska-Lincoln, Lincoln, NE, USA;(3) School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, NE, USA;(4) Department of Crop and Soil Sciences, Cornell University, Ithaca, NY, USA;(5) Department of Agronomy and Horticulture, University of Nebraska-Lincoln, Lincoln, NE, NE |
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Abstract: | Results of a previous 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 chemical 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 34N44 Bt and NC+ 4990 Bt) and their non-Bt isolines
(Pioneer 34N43 and NC+ 4880) were analyzed for biomass fractions (soluble, hemicellulose, cellulose, and lignin) 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 and mass of C remaining over time between the Bt and non-Bt corn residues. Plant parts differed
in decomposition rates where leaves > stalks > cobs. There were differences in total C, total N, biomass fractions, and C:N
ratios between initial 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 or mass of C remaining over time. 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. |
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Keywords: | Decomposition Bt Corn Biomass Biomass fraction Lignin Soluble Cellulose Hemicellulose |
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