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Title: EFFECTS OF GLYPHOSATE DRIFT ON NITROGEN FIXATION POTENTIAL OF A GLYPHOSATE SENSITIVE SOYBEAN CULTIVAR

Author
item Zablotowicz, Robert
item Reddy, Krishna
item Bellaloui, Nacer

Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 2/6/2006
Publication Date: 2/6/2006
Citation: Zablotowicz, R.M., Reddy, K.N., Bellaloui, N. 2006. Effects of glyphosate drift on nitrogen fixation potential of a glyphosate sensitive soybean cultivar. Weed Science Society of America Meeting Abstracts. 329

Interpretive Summary:

Technical Abstract: Non-target injury to conventional crops from glyphosate drift is a concern among growers using non-glyphosate-resistant cultivars. The effects of glyphosate drift on nitrogen fixation potential of glyphosate sensitive soybean were assessed in a field trial in 2005 at Stoneville, MS. A non-glyphosate-resistant soybean cultivar Delta Pine 4748S was planted with corn grown on all sides of the experimental plots to minimize spray drift from glyphosate applications. A single application of glyphosate at 12.5% of use rate of 0.84 kg ae/ha was applied at 3, 6, and 8 (full bloom) weeks after planting (WAP) soybean to simulate glyphosate drift. Soybeans were sampled at 4, 5, 7, 8, 9 and 10 WAP and assessed for root, shoot and nodule weight, N2 fixation potential using the acetylene reduction assay (ARA), and nitrogen content of shoots and soybean seed. At 10 WAP, significant reductions in root and shoot biomass were observed for all three ttreatments. No consistent effect of glyphosate on nodulation was observed. Specific ARA activity was reduced 36 to 58% by glyphosate treatment at 3 or 6 WAP for two or four weeks after application. However, no effect on specific ARA activity was observed during the last two samples. Likewise, shoot, or leaf nitrogen content was only affected by glyphosate application after the first application. These results suggest that nitrogen fixation potential was significantly reduced by glyphosate drift and the greatest sensitivity during early in vegetative growth. Thus soybean has the ability to recover from this physiological stress caused by glyphosate drift.