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United States Department of Agriculture

Agricultural Research Service

Research Project: Improving Nutrient Utilization in Western Irrigated Crop Production Systems

Location: Northwest Irrigation and Soils Research

Title: In-field rates of decomposition and microbial communities colonizing residues vary by depth of residue placement and plant part, but not by crop genotype for residues from two Cry1AB Bt corn hybrids and their non-transgenic i

Authors
item Londono-R, Luz Marina -
item Tarkalson, David
item Thies, Janice -

Submitted to: Soil Biology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 10, 2012
Publication Date: February 1, 2013
Citation: Londono-R, L., Tarkalson, D.D., Thies, J.E. 2013. In-field rates of decomposition and microbial communities colonizing residues vary by depth of residue placement and plant part, but not by crop genotype for residues from two Cry1AB Bt corn hybrids and their non-transgenic isolines. Soil Biology and Biochemistry. 57(2013):349-355.

Interpretive Summary: The adoption of biotech crops engineered to produce a bacterial protein (Bt) that is toxic to specific crop pests has been largely overshadowed by concerns about their unintended effects on human health and the environment. Residues of Bt crops decomposed more slowly than their unaltered parental varieties in one laboratory study, although no mechanism to explain these observations was proposed. If Bt crop residues were to decompose more slowly in field soils, changes in carbon cycling and nutrient availability could result. This study compared the in-field decomposition rates and diversity of decomposers colonizing residues of two Bt corn hybrids, active against the European corn borer, with their unaltered parental varieties in litterbags placed in a Nebraska field. After five months, we found no differences in either the rates of residue mass loss or in the decomposers colonizing the Bt-corn residues versus the residues from the parental varieties. Instead, both residue mass loss and colonizing communities were significantly affected by residue placement (surface versus buried) and plant part, demonstrating that environmental factors and residue quality, not the presence of the Bt toxin, were the key drivers of residue decomposition and decomposer colonization in this study.

Technical Abstract: The adoption of Bt corn has been largely overshadowed by concerns about their unintended effects on human health and the environment. Residues of transgenic Bt crops decomposed more slowly than their non-transgenic isolines in one laboratory study, although no mechanism to explain these observations was proposed. If Bt crop residues were to decompose more slowly in field soils, changes in carbon cycling and nutrient availability could result. We compared the in-field decomposition rates and diversity of decomposers colonizing residues of two Cry1Ab Bt corn hybrids, active against the European corn borer, with their non-transgenic isolines in litterbags placed in a Nebraska field. After five months, we found no significant differences in either the rates of residue mass loss or in the bacterial, fungal or microarthropod communities colonizing the transgenic versus the non-transgenic residues. Instead, both residue mass loss and detritivore colonizers were significantly affected by residue placement (surface versus buried) and plant part, demonstrating that environmental factors and residue quality, not the presence of the Cry1Ab protein, were the key drivers of residue decomposition and detritivore colonization in this study.

Last Modified: 7/23/2014