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ARS Home » Plains Area » Temple, Texas » Grassland Soil and Water Research Laboratory » Research » Publications at this Location » Publication #204413

Title: Soil microbial activity is affected by Roundup WeatherMax and pesticides applied to cotton (Gossypium hirsutum)

item Haney, Richard

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/27/2006
Publication Date: 8/25/2006
Citation: Lancaster, S.H., Haney, R.L., Senseman, S.A., Hons, F.M., Chandler, J.M. 2006. Soil microbial activity is affected by Roundup WeatherMax and pesticides applied to cotton (Gossypium hirsutum). Journal of Agricultural and Food Chemistry. 54(19):7221-7226.

Interpretive Summary: From an environmental perspective, the use of the herbicide Roundup would be preferred over other herbicides since it is rapidly destroyed by soil microbes. However, Roundup-based weed control systems have resulted in extensive use of the herbicide, with multiple applications in a single growing season becoming common. Roundup is also applied with other pesticides and may affect the ability of soil microbes to break them down into harmless chemical compounds. This research indicates that soil microbes are very sensitive to chemicals added to the soil and that soil microbial activity can be very useful when assessing the impact these chemicals will have on the longer-term health of the soil. Soil microbial activity rapidly identified (within a few days) which combinations of herbicides and pesticides that had the potential to alter the soil microbe’s ability to rapidly destroy these chemical inputs.

Technical Abstract: Adoption of glyphosate-based weed control systems has led to increased use of the herbicide with continued use of additional pesticides. Combinations of pesticides may affect soil microbial activity differently than pesticides applied alone. Research was conducted to evaluate the influence of glyphosate-based cotton pest management systems on soil microbial activity. Soil was treated with commercial formulations of trifluralin, aldicarb, and mefenoxam + pentachloronitrobenzene (PCNB) with or without glyphosate (applied as Roundup WeatherMax). The soil microbial activity was measured by quantifying C and N mineralization. Soil microbial biomass was determined using the chloroform fumigation-incubation method. Soils treated with glyphosate alone exhibited greater cumulative C mineralization 30 days after treatment than all other treatments, which were similar to the untreated control. The addition of Roundup WeatherMax reduced C mineralization in soils treated with fluometuron, aldicarb, or mefenoxam + PCNB formulations. These results indicate that glyphosatebased herbicides alter the soil microbial response to other pesticides.