Dick_R Influence of Long-term Use of Glyphosate


Influence of Long-term Use of Glyphosate on Microbial Communities and Bioavailability of Potassium

Funding Agency: Ag Spectrum and Ohio Soybean Council 
Postdoctoral Researcher: Dr. Nicola Lorenz
MS Graduate Student: Matt Lane
Glyphosate tolerant soybean (GTS) technology is a valuable asset for soybean farmers because it reduces the use of other herbicides, is a critical weed control tool for reduced tillage systems, and is generally regarded as having low environmental impacts. However, after applying this technology for up to 10 years, observations in farmers’ fields and emerging research suggest that long-term glyphosate usage is having cumulative and non-target effects on soils and crop productivity. In recent years there has been research confirmation of Mn deficiency in glyphosate tolerant crops and now a growing incidence of potassium (K) deficiency in corn when grown in rotation with GTSs in the upper Midwest. With the increasing use of glyphosate tolerant corn these non-target effects will likely be further magnified. Based on preliminary research and limited evidence from the literature, we hypothesize that glyphosate causes a microbial shift toward fungal dominance or specific fungal genera, which rapidly take up K and transfer it to non-exchangeable/plant unavailable forms. To address this we are proposing a series of investigations that include: Obj. 1, an on-farm study of GTS systems to track soil microbial community composition and K soil pools and biological K immobilization in GTS fields having a history of K deficiency; and Obj. 2, a series of mechanistic lab studies to determine whether glyphosate and GTS plant residue added to soil alters microbial community composition and causes transformation of K to unavailable forms in soil minerals or soil organic matter. The outcomes of this research will provide a basis to predict potential non-target impacts of repeated  use of glyphosate and to develop recommendations to maintain the long-term viability of GTS technology.
Dr. Richard P. Dick
School of Environment and Natural Resources
210 Kottman Hall
Ohio State University
Columbus OH 43210
PHONE: 614.247.7605
FAX: 614.292.7432