Graduate Thesis Or Dissertation
 

The response of nitrifying bacteria to treatments of N-Serve and Roundup in continuous-flow soil columns

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/f7623g23j

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  • This study examined the effects of Roundup [N-(phosphonomethyl) glycine] and N-Serve [2-chloro-6- (trichloromethyl) pyridine] on nitrifying organisms in static batch, perfusion soil columns, and a new continuous-flow soil column system. The continuous-flow method is new to nitrification studies and was shown to produce greater nitrifier activity than either static batch of perfusion techniques. Both N-Serve and Roundup were shown to significantly inhibit nitrification in treated soils over untreated controls. N-Serve completely inhibited nitrification at concentrations greater than 42 ug nitrapyrin g⁻ ¹ dry soil. Roundup significantly reduced nitrification at 6.8 and 68 mg glyphosate g⁻ ¹ dry soil. Continuous-flow columns were examined to determine if microbial populations were altered by chemical treatment. Concentrations of 4.2 mg nitrapyrin and 68 mg glyphosate g⁻ ¹ dry soil significantly increased heterotrophic populations. Numbers of heterotrophs were not significantly different from controls in soils at lower concentration. Numbers of nitrifying bacteria did not appear to change following treatment although nitrification was inhibited. Fluorescent antibody analysis of nitrifiers revealed that Nitrosolobus was more numerous than Nitrosospira and Nitrosomonas. Nitrosolobus increased in number whereas the other two genera remained unchanged. In this study, the continuous-flow system proved to be both reliable and useful in the culture of nitrifying bacteria. This method is an alternative to traditional techniques for evaluation of the effects of chemicals on microbial biogeochemical cycles.
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