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United States Department of Agriculture

Agricultural Research Service

Research Project: Integrated Strategies for Improved Water Quality and Ecosystem Integrity within Agricultural Watersheds

Location: Water Quality and Ecology Research

Title: Impact of glyphosate resistant corn and glyphosate applications under conventional and reduced tillage practices on exoenzyme activities and microbial community structure of bulk and rhizosphere soils

Authors
item Jenkins, Michael
item Locke, Martin
item Reddy, Krishna
item McChesney, Daniel
item Steinriede, Robert

Submitted to: American Society for Microbiology General Meeting
Publication Type: Abstract Only
Publication Acceptance Date: March 21, 2014
Publication Date: N/A

Interpretive Summary: Abstract only.

Technical Abstract: Background Conservation tillage practices across the country have been implementing genetically engineered glyphosate resistant corn crops along with applications of the herbicide glyphosate. We tested the hypothesis that six years of glyphosate applications to both resistant and non-resistant corn under reduced and conventional tillage would impact key soil exoenzymes involved in mineralization and their associated soil microbial community. Method The experimental design was a randomized complete block with glyphosate resistant (GR) and non-GR corn, with and without glyphosate applications under reduced and conventional tillage. Bulk and rhizosphere soil samples were analyzed for four initial mineralizing exoenzymes, ß-glucosidase (BG), ß-N-acetylglucosaminidase (NAG), leucine aminopeptidase (LAP), acid phosphatase (AP), and for fluorescein diacetate (FDA) hydrolysis as a measure of total microbial activity. DNA extracted from corn rhizosphere and adjacent bulk soils and 16sRNA genes from bacterial and archaeal components of both soil microbial communities were sequenced with Illumin’s MiSeq platform and with Roche 454 FLX sequencer machine, respectively. Sequences were analyzed with MOTHUR. Results Excepting FDA, differences (at P < 0.05) in mean BG, AP, NAG, and LAP activities were observed for both soil types and tillage practice. Preliminary sequence analyses indicate significant differences in community structure between soil types and tillage practices Conclusions Interactions between treatments and tillage practices appeared to impact exoenzyme activities. Preliminary analyses of 16sRNA genes indicate that soil type and tillage as major factors affecting microbial community structure.

Last Modified: 12/19/2014
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