| The conversion of weed control methods from conventional herbicide applications to the use of a single herbicide (glyphosate) has created new research opportunities in both crop and soil science. Concerns have arisen with respect to soil bioavailability of manganese (Mn) and potential complexation in glyphosate-resistant crops. Both greenhouse and field studies were conducted in the spring and summer of 2011 to investigate whether glyphosate reduced soybean uptake of Mn. Each experiment used soil from the James C. Hageman Sustainable Agriculture and Research Extension Center (SAREC) near Lingle, WY. Each trial lasted approximately 10 weeks, and harvested plants were subjected to tissue Mn analysis, biomass production, chlorophyll concentration and seed yield. Laboratory experiments were performed to examine soil solution sorption chemistry of Mn, glyphosate, and the Mn-glyphosate complex. In separate experiments, total soil Mn, bioavailable fraction, and labile concentrations were analyzed to evaluate soil solution dynamics both separately and in conjunction with the herbicide. Glyphosate rates generally proved to be insignificant in complexing Mn and causing plant deficiencies. Manganese tissue concentration, seed yield, biomass production and chlorophyll ratings showed no treatment differences. Significance was primarily found between varieties. Both the greenhouse experiment and field trials had a late-maturing variety (of the varieties randomly chosen for each trial), which consistently demonstrated poor growth, chlorophyll concentration, and decreased seed yield as opposed to the other varieties. |
