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THE EFFECT OF GLYPHOSATE ON SOIL MICROBIAL COMMUNITIES

Lane, Matthew S.
http://rave.ohiolink.edu/etdc/view?acc_num=osu1301068421

Abstract Details

2011, Master of Science, Ohio State University, Soil Science.
Glyphosate [N-(phosphonomethyl)glycine] is the most widely used herbicide in the world. First sold in 1974 under the trade name Roundup, its use has increased dramatically in recent years with the introduction of genetically modified, glyphosate resistant (GR) crops. There is growing anecdotal evidence in the Midwestern United States of potassium (K) deficiency in corn, which appears to be related to the adoption of GR soybeans grown in rotation with corn. It is possible that the use of glyphosate in GR cropping systems is creating a selection pressure in soil microbial communities which could affect soil K dynamics. The first objective of Chapter 1 was to determine the effect of rates of glyphosate on microbial respiration. The second thesis objective of Chapter 1 was to determine the effect of glyphosate on microbial community structure, exchangeable, non-exchangeable, and microbial K in soils that had no, limited, or high amounts of glyphosate exposure under field conditions. The objectives of Chapter 2 were to determine the effect of foliar glyphosate applied to GR soybean on: 1) the rhizosphere soil microbial community composition, 2) exchangeable, non-exchangeable, and microbial K; and 3) leaf concentration K. In an incubation experiment, the addition of glyphosate was shown to significantly increase microbial respiration rates. The magnitude and duration of rates of respiration were greater in soils with a previous history of glyphosate applications, indicating that previous exposure to glyphosate may be associated with an increase in organisms able to metabolize glyphosate. In a second experiment, glyphosate was applied repeatedly to soils over a 180 day period. There were no significant shifts in soil microbial community structure based on ester linked fatty acid methyl ester (EL-FAME) analysis. In addition, glyphosate application did not significantly affect microbial biomass K. In a third experiment, glyphosate resistant soybeans grown in the greenhouse were exposed to repeated glyphosate applications. Glyphosate application did cause a significant decrease in the total microbial biomass in soybean rhizosphere soil, as measured by total extracted EL-FAMEs, in the soil that had no previous exposure to glyphosate at seven days after the glyphosate application. However, no significant changes were observed in the overall microbial community structure. These studies indicated that: 1) glyphosate stimulates microbial respiration; 2) repeated glyphosate application to soil may increase populations of microorganisms able to degrade glyphosate; 3) the application of glyphosate can lower total microbial biomass in the glyphosate resistant soybean rhizosphere; 4) changes in the structural diversity of the soil microbial community due to glyphosate application were not detectible using EL-FAME profiling, and; 5) glyphosate does not appear to reduce the plant availability of K, as no significant decreases in exchangeable or plant tissue K, nor increases in microbial biomass K, were observed after glyphosate application.
Richard Dick, PhD (Advisor)
Brian McSpadden Gardener, PhD (Committee Member)
Ed McCoy, PhD (Committee Member)
83 p.
Agronomy; Environmental Science; Soil Sciences
Glyphosate; EL-FAME; FAME; fatty acid methyl esters

Recommended Citations

Citations

  • Lane, M. S. (2011). THE EFFECT OF GLYPHOSATE ON SOIL MICROBIAL COMMUNITIES [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1301068421

    APA Style (7th edition)

  • Lane, Matthew. THE EFFECT OF GLYPHOSATE ON SOIL MICROBIAL COMMUNITIES. 2011. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1301068421.

    MLA Style (8th edition)

  • Lane, Matthew. "THE EFFECT OF GLYPHOSATE ON SOIL MICROBIAL COMMUNITIES." Master's thesis, Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1301068421

    Chicago Manual of Style (17th edition)

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This open access ETD is published by The Ohio State University and OhioLINK.