Graduate Defense Seminar

Feb 20, 2014, 11:00am - 11:30am


A Graduate Defense Seminar will be given by Mark Nye (ESPG) in 202F Kottman Hall. His presentation will be Microbial Diversity in Simulated Long-term Glyphosate Tolerant Cropping Systems.

Glyphosate is a broad-spectrum herbicide used throughout the world to control broadleaf weeds in agricultural scenarios. Research suggests that repeated application causes a change in soil microbial ecology which may affect soil fertility and subsequently the suitability of soil to grow crops. Glyphosate tolerant (GT) soybean technology is a valuable asset for farmers because it reduces the use of other herbicides, acts as a critical weed control tool for reduced tillage systems, and is generally regarded as having low environmental impacts. However, after using this technology for 10 or more years, field observations by farmers and emerging research suggest that long-term glyphosate usage is having cumulative non-target effects on soils and crop productivity.

Limited short-term research suggests that glyphosate application causes changes in soil microbial ecology which may be detrimental to plant growth and health. However, now that these systems have been in use for more than 15 years, there is anecdotal evidence that long-term repeated application of glyphosate has a detrimental effect on crop yields, including non-GT plants.

Therefore, the objective of this study was to analyze soil microbial communities during decomposition of biomass from plants grown in soil that have been exposed to glyphosate in soils with and without a history of glyphosate exposure. An experiment was designed to condense 8 years of field applications into 24 months in the greenhouse. Soybean residues from this experiment were used in an laboratory incubation study utilizing soils with and without a history of glyphosate exposure. The diversity of microbial populations from these soils was assessed by analysis of PLFAs to identify shifts in soil microbial community structure. The results of this study showed that there is a significant difference between the microbial communities during decomposition of plant residue based on the individual soil’s history of glyphosate exposure, and that furthermore the communities change differently within each soil based on type of residue, time, and plant exposure to glyphosate.