Monoammonium Phosphate Effects on Glyphosate in Soils: Mobilization, Phytotoxicity, and Alteration of the Microbial Community

Application of monoammonium phosphate has been demonstrated to re-immobilize glyphosate sorbed by soil under model laboratory experiment conditions. This effect was most pronounced in the gray forest soil (Haplic Phaeozem), where the concentration of herbicide in the presence of fertilizer was 3.6 times higher than in its absence. For soddy-podzolic soil (Albic Retisol) and leached Chernozem (Luvic Chernozem), this ratio was 1.5 and 2.8, respectively. Thus, the introduction of monoammonium phosphate into soils contaminated with glyphosate may result in an increase of the risk of herbicide migration into the neighboring environments. The estimated number of functional genes of bacteria responsible for glyphosate degradation by means of the C–P bond cleavage did not show statistically significant effect of the fertilizer on the number of copies of the phnJ gene, encoding the C–P lyase of α- and γ-proteobacteria. The release of glyphosate was not accompanied by any adverse effects on the length and biomass of wheat plants.