Microbial dynamics in soils under long-term glyphosate tolerant cropping systems

摘要

Glyphosate is a non-selective, broad-spectrum herbicide now widely used. Early research on short-term effects on soil microbiology was inconclusive, but now long-term applications of glyphosate to tolerant cropping (GTC) systems may be shifting microbial communities and causing plant nutrition deficiencies and diseases. A field survey of 10 pairs of fields (K sufficient and deficient) under >10 yrs GTC showed significant negative correlations between microbial biomass K and K crop uptake suggesting glyphosate applications caused microbial immobilization of K. A 28 day experiment with a single glyphosate application and another experiment with repeated glyphosate application was done on soils from >10 yrs GTC or soils that had never received glyphosate The soils that had been under GTC showed no shift in fatty acid profiling of microbial communities (suggesting they had adapted) compared to the non-GTC soils where unique fatty acids were stimulated by the addition of glyphosate. For example, gram positive bacteria responded to glyphosate in non-GTC soils but not GTC soils. This suggested that adding glyphosate does cause a shift in a sub population of the soil. DNA-DGGE analysis of GTC fields identified Fusarium species that are known to be pathogenic. The results suggest there is sub-population shift that is occurring with long-term GTC.