PARENT SESSION
Contributed Oral Session 109: Agroecology: Soils; Nutrient Cycling
Thursday, August 11, 8:00 AM - 11:30 AM, Meeting Room 513 A, Level 5, Palais des congrès de Montréal
Impact of Coleopteran-active Bt corn on of nontarget decomposition process and saprophytic microbial communities.
Lawhorn, C.N.*,1, Neher, D.A.2, Dively, G.P.3, 1 University of Toledo, Toledo, OH2 Department of Plant and Soil Science, Burlington, VT3 Department of Entomology, College Park, MD
ABSTRACT- Soil microbial communities are potentially exposed to Cry3Bb1 toxins exudated from living or decaying roots of Bt corn (event MON863, YieldGard® Rootworm) targeted for corn rootworms. Our objective was to determine whether coleopteran-Bt corn affected nontarget ecological processes such as decomposition and associated saprophytic microbial community. Crop treatments were a 1) Bt hybrid, 2) non-Bt, isogenic hybrid treated with a soil insecticide, and 3) a non-Bt, isogenic hybrid without insecticide. Treatment plots (0.2 ha) were established in a non-till field and replicated three times in a Latin square design. Litter bags were buried at the time of root senescence (immediately after anthesis) and bags were collected and analyzed at 1, 2 and 3 months thereafter and two times in spring months, before planting the next crop. Rate of decomposition and extracellular enzyme activity (EEA) was quantified for decomposing root tissue in litter bags constructed of saran mesh (26 x 14 cm; 1 mm by 1.5 mm mesh size). Generally, seasonal affects were greater than crop affects for decomposition rates and microbial community dynamics. Significantly different enzyme activity levels over sampling times were expected because it is understood that there are different rates for activity levels throughout the process of decomposition. This is one of the first reports to quantify nontarget impacts of coleopteran-active Bt corn on decomposition processes in field conditions. These results represent a subset of a larger experiment to quantify impacts of Coleopteran-active Bt corn on multiple trophic levels in soil and litter communities.
Key words: BT corn, decomposition, microbial communities, extracellular enzyme activity