Soil microbial communities in diverse agroecosystems exposed to glyphosate

Abstract

24In spite of glyphosate's wide use in agriculture, questions remain about effects of the herbicide 25 on soil microbial communities. Conflicting scientific literature reports divergent results; from no 26 observable effect of glyphosate to the enrichment of common agricultural pathogens such as 27Fusarium. We conducted a comprehensive field-based study to compare treatments that did 28 and did not receive foliar application of glyphosate spray. The study included two field sites, 29Maryland and Mississippi; two crops, soybean and corn; four site years, 2013 and 2014; and a 30 variety of organic and conventional farming systems. Using amplicon sequencing, the 31 prokaryotic (16S rRNA) and fungal (ITS) communities were described along with chemical and 32 physical properties of the soil. Sections of corn and soy roots were plated to screen for the 33 presence of plant pathogens. Geography, farming system, and seasonal progression were 34 significant factors determining composition of fungal and bacterial communities. Plots treated 35 with or without glyphosate did not differ in overall microbial community composition after 36 controlling for these factors. No differential effect of glyphosate treatment was found in the 37 relative abundance of organisms such as Fusarium spp. or putative growth-promoting bacteria 38