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United States Department of Agriculture

Agricultural Research Service

Research Project: Mitigating Agricultural Sources of Particulate Matter and Greenhouse Gas Emissions in the Pacific Northwest

Location: Northwest Sustainable Agroecosystems Research

Title: Soil microbial community response to surfactants and herbicides in two soils

Authors
item Banks, Mona -
item Kennedy, Ann
item Kremer, Robert
item Eivazi, Frieda -

Submitted to: Applied Soil Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 28, 2013
Publication Date: December 15, 2013
Citation: Banks, M.L., Kennedy, A.C., Kremer, R.J., Eivazi, F. 2013. Soil microbial community response to surfactants and herbicides in two soils. Applied Soil Ecology. 74: 12–20.

Interpretive Summary: The impact of herbicides on more than just weeds is of environmental interest. Surfactants often used with herbicides may also effect soil life. We used a silt loam and a silty clay loam from south central Missouri to investigate the impact of herbicides and surfactants on the soil microbial activity. The soils differed in some chemical and microbial characteristics and in microbial response to treatments. Most of the herbicides and surfactants used in this study did not greatly change the microbial community. A few treatments altered components of the microbial community after only one application of fieldrate chemicals. These changes varied with soil texture and compound. Whether these changes are biologically significant, either positive or negative, is not known. Further long-term studies are needed to determine additional changes in the microbial community after several years of annual applications of herbicides and surfactants. Further long-term studies conducted by the scientific community across the nation are needed to determine additional changes or lack of change in the microbial community after several years of annual applications of herbicides and surfactants. This research can be used by scientists, industry personnel and the public to assess the impact of various herbicides and surfactants on soil life.

Technical Abstract: The impact of herbicides on more than just the target weed and the effect of some herbicides on the soil biota is of environmental interest. The surfactants that are often used with herbicides are also coming under fire as a potential harm to the soil life. We used a silt loam and a silty clay loam from south central Missouri to investigate the impact of herbicides and surfactants on the soil microbial activity. The surfactants used in this study were alkylphenol ethoxylate plus alcohol ethoxylate (Activator 90), polyethoxylate (Agri-Dex) and a blend of ammonium sulfate, drift reduction/deposition polymers and anti-foam agent (Thrust). The herbicides were glyphosate (Gly-4 Plus), atrazine (Atrex) and bentazon (Basagran). Surfactants and herbicides were applied to soils at label rate, either alone or in combination, to 4000 g soil per pot. Untreated silt loam and untreated silty clay loam from south central Missouri differed in texture, some chemical characteristics and several microbial community characteristics. A few of the chemicals altered some of the components of the microbial community after only one application of field-rate amounts of chemicals. The silt loam, however, showed larger differences in changes in the microbial community with application of treatments. Few changes were seen in the PLFA markers or patterns in the silty clay loam except for polyethoxylate and bentazon treatments that increased microbial biomass; Thrust that decreased BtoF; and Agri at both rates that decreased monounsaturated fatty acids. Changes in the microbial community due to herbicides or surfactants were minimal in this study of a one-time application. Further long-term studies are needed to determine the changes in the microbial community after several years of annual applications of herbicides and surfactants.

Last Modified: 10/20/2014
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