DISCOVERY AND DEVELOPMENT OF NATURAL PRODUCT-BASED WEED MANAGEMENT METHODS
Location: Natural Products Utilization Research
Title: Effects of glyphosate on mineral content of glyphosate-resistant soybeans (Glycine max)
Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 25, 2012
Publication Date: June 28, 2012
Citation: Duke, S.O., Reddy, K.N., Bu, K., Cizdziel, J.V. 2012. Effects of glyphosate on mineral content of glyphosate-resistant soybeans (Glycine max). Journal of Agricultural and Food Chemistry. 60:6764-6771.
Interpretive Summary: There has been recent controversy about whether glyphosate causes mineral deficiencies in glyphosate-resistant crops. Three groups have reported effects and nine others have found no effects. None of these previous studies examined more than a few minerals. In this paper, glyphosate-resistant soybean plants were treated with one or two recommended doses of glyphosate in both greenhouse and field studies. Non-treated plants were used as a control. After application, young and older leaves were sampled at three (greenhouse) or two (field) times. Seeds were sampled from mature plants. These samples were analyzed for 13 (leaves) or 14 (seed) minerals. Minerals tested were calcium, magnesium, manganese, zinc, iron, copper, strontium, barium, aluminum, cadmium, chromium, cobalt, nickel, and selenium. No effects of any of the treatments on content of any of the minerals were seen in any of the samples. There was no effect of glyphosate on seed yield. These results support the view that glyphosate has no effect on mineral content of glyphosate-resistant soybean when used at recommended application rates.
There are conflicting claims as to whether treatment with glyphosate adversely affects mineral nutrition of glyphosate-resistant (GR) crops. Those who have made claims of adverse effects have argued links between reduced Mn and diseases in these crops. This paper describes experiments designed to determine the effects of a recommended rate (0.86 kg ha-1) of glyphosate applied once or twice on the mineral content of young and mature leaves, as well as in seeds produced by GR soybeans (Glycine max) in both the greenhouse and field using inductively coupled plasma mass spectrometry (ICP-MS). In the greenhouse, there were no effects of either one application (at 3 weeks after planting, WAP) or two applications (at 3 and 6 WAP) of glyphosate on Ca, Mg, Mn, Zn, Fe, Cu, Sr, Ba, Al, Cd, Cr, Co, or Ni content of young or old leaves sampled at 6, 9, and 12 WAP and in harvested seed. Se concentrations were too low for accurate detection in leaves, but there was also no effect of glyphosate applications on Se in the seeds. In the field study, there were no effects of two applications (at 3 and 6 WAP) of glyphosate on Ca, Mg, Mn, Zn, Fe, Cu, Sr, Ba, Al, Cd, Cr, Co, or Ni content of young or old leaves at either 9 or 12 WAP. There was also no effect on Se in the seeds. There was no difference in yield between control and glyphosate-treated GR soybeans in the field. The results indicate that glyphosate does not influence mineral nutrition of GR soybean at recommended rates for weed management in the field. Furthermore, the field studies confirm the results of greenhouse studies.