Understanding the chemistry of manganese fertilizers and glyphosate mixtures by using synchrotron X-ray spectrometry

Abstract

The spraying of tank mixtures with manganese (Mn) and glyphosate is a practical alternative to alleviate nutritional deficiency while controlling weeds. Thereby, this study investigates the chemical interactions between glyphosate and commercial sources of Mn, such as MnSO 4 , Mn-phosphite, Mn-EDTA, Mn-glycine, and MnCO 3. Nearly 30% of the Mn supplied as MnSO 4 and Mn-glycine precipitated with glyphosate, yielding a Mn:glyphosate solid complex with molar ratio of nearly 2:1, both presenting similar chemical environment. XANES analysis of the supernatants indicate no formation of Mn-glyphosate soluble complexes. The use of Mn-EDTA as well as the maintenance of the mixture pH below 2.5 prevented precipitation, while pH above 7 caused the formation of MnO(OH). In conclusion, the Mn source and the pH of the mixtures matter. The absence of Mn-glyphosate soluble complexes suggests that dissolved Mn and glyphosate are still able to accomplish their functions, however, the precipitation significantly decreases their active availability.

Enhancing the efficiency and sustainability of foliar fertilization in agriculture

“…Fourthly, the mixture of different products with nutrients without proper protection (chelation or complexation) may lead to tank reactions. These reactions can diminish the performance of products and, in extreme cases, result in clogs in the sprayer system (Machado et al, 2020), leading to financial losses for farmers and exacerbating environmental problems.…”

“…However, it is essential to know which fertilizer will be used and with which products it will be mixed, especially when dealing with pesticides. Glyphosate, for instance, has its performance increased when applied through a spraying medium with a pH lower than 4.0 (Machado et al, 2020). Conversely, fungicides, such as the commercial product named FOX SC325®, work better at a pH ranging from 5.5 to 7.0.…”