Impact of glyphosate herbicide on some soil biology and function

Abstract

Soil microbiotas regulate the bioprocesses in soil that are essential for plant growth, soil health and sustained productivity. Despite an increasing concern of consequences of using vast amounts of Glyphosate- based herbicides in agroecosystems, their potential effects on non-target soil organisms and soil functioning are mostly unknown. Application of herbicides may not affect the overall size of the soil microbiotas but selectively can effect on specific microbial groups which may result in changing the balance of bioactivity and consequently nutrient availability, disease incidence and plant growth. Glyphosate is a broad-spectrum, non-selective and post-emergence herbicide, used as an active ingredient in several weed killing products since 1970s. Glyphosate is also vulnerable to microbial degradation and its main degradation product, aminomethylphosphonic acid, is strongly adsorbed to soil solids. For these reasons, Glyphosate has generally been regarded as an environmentally safe herbicide. In the current study, N2-fixing soil microbial populations and their activities were determined in microcosms under the stress of Glyphosate herbicide were applied at 3 doses based on the active ingredients and incubated for 10 weeks at 28°C. Results indicated that: Application of Glyphosate had negative impact on symbiotic N2-fixation by legumes in rotation and application of a post-emergent herbicide caused significant changes in the microbial community and the activities of some hydrolytic enzymes in the rhizosphere. Impacts of Glyphosate on rhizosphere microorganisms and activities were investigated. Information on the effects of herbicide application on useful soil microbiotas and their bioprocesses is necessary for the successful crop production. A particular practices may have the desired result in one situation but have little effect in another because biological communities respond to the interaction of multiple factors including food sources, physical habitat, moisture, and impacts of historical land use. Therefore, before a new product is applied to a field soil, it should be tested on a limited area and the results should be monitored in comparison to an untreated one.

Soil microbiotas regulate the bioprocesses in soil that are essential for plant growth, soil health and sustained productivity. Despite an increasing concern of consequences of using vast amounts of Glyphosate- based herbicides in agroecosystems, their potential effects on non-target soil organisms and soil functioning are mostly unknown. Application of herbicides may not affect the overall size of the soil microbiotas but selectively can effect on specific microbial groups which may result in changing the balance of bioactivity and consequently nutrient availability, disease incidence and plant growth. Glyphosate is a broad-spectrum, non-selective and post-emergence herbicide, used as an active ingredient in several weed killing products since 1970s. Glyphosate is also vulnerable to microbial degradation and its main degradation product, aminomethylphosphonic acid, is strongly adsorbed to soil solids. For these reasons, Glyphosate has generally been regarded as an environmentally safe herbicide. In the current study, N2-fixing soil microbial populations and their activities were determined in microcosms under the stress of Glyphosate herbicide were applied at 3 doses based on the active ingredients and incubated for 10 weeks at 28°C. Results indicated that: Application of Glyphosate had negative impact on symbiotic N2-fixation by legumes in rotation and application of a post-emergent herbicide caused significant changes in the microbial community and the activities of some hydrolytic enzymes in the rhizosphere. Impacts of Glyphosate on rhizosphere microorganisms and activities were investigated. Information on the effects of herbicide application on useful soil microbiotas and their bioprocesses is necessary for the successful crop production. A particular practices may have the desired result in one situation but have little effect in another because biological communities respond to the interaction of multiple factors including food sources, physical habitat, moisture, and impacts of historical land use. Therefore, before a new product is applied to a field soil, it should be tested on a limited area and the results should be monitored in comparison to an untreated one.