Skip to main content
ARS Home » Southeast Area » Auburn, Alabama » Soil Dynamics Research » Research » Publications at this Location » Publication #278396
Title: Response of cogongrass genotypes to glyphosate under field and greenhouse conditions

Author
item AULAKH, J - Auburn University
item ENLOE, S - Auburn University
item Price, Andrew
item VAN SANTEN, EDZARD - Auburn University

Submitted to: Proceedings of Southern Weed Science Society
Publication Type: Abstract Only
Publication Acceptance Date: 2/25/2012
Publication Date: 2/25/2012
Citation: Aulakh, J.S., Enloe, S.F., Price, A.J., Van Santen, E. 2012. Response of cogongrass genotypes to glyphosate under field and greenhouse conditions. Proceedings of Southern Weed Science Society. CDROM.

Interpretive Summary:

Technical Abstract: A field project was conducted from spring 2007 through fall 2010 to evaluate Cogongrass genotype response to soil fertility and glyphosate treatment. The experimental site had been a long–term soil fertility study since 1929. The long–term fertility treatments consisted of six rates of nitrogen, three rates of phosphorus and five rates of potassium. Six Cogongrass genotypes were evaluated. Glyphosate (4 lb/acre) was applied as a strip treatment in October 2008 and again in 2009. Additionally, two runs of complementary greenhouse experiment were conducted from 2009 through 2010 to evaluate dose response relationship using six different rates of glyphosate across six Cogongrass genotypes. Glyphosate was applied inside a spray chamber at 0.5, 1.0, 2.0, 3.0, 4.0 and 8.0 lb/a at 20 gpa to about 140 days old Cogongrass. The results from field research indicated no effect of phosphorus rates, a linear decrease in rhizome dry weight with increase in nitrogen rates, and an increase with increase in potassium. Cogongrass genotypes differed for %TNC content and maximum alive-rhizome depth. Red Baron genotype recorded a significantly lower rhizome dry weight, alive-rhizome depth and % TNC content than other five Cogongrass genotypes. These results indicate that Cogongrass did not benefit by increased nitrogen and phosphorus fertilization but did respond positively to increased potassium with respect to rhizome dry weight only. Maximum alive-rhizome depth and % TNC were unaffected by nitrogen, phosphorus and potassium. Glyphosate resulted in a uniform decrease in Cogongrass cover in all the biotypes but all of them recovered at least 20% growth a year after treatment. There was some indication of differential recovery among genotype with Auburn genotype recovering much faster than others. Greenhouse research also indicated differential response of Cogongrass genotypes to different glyphosate rates. Dose response curves revealed significant difference in LD90 for Cogongrass genotypes. LD90 was 1.7 lb/a for Auburn and Mobile, about 1 lb/a for Louisiana, Florida and B genotypes and 4.8 lb/a for Red Baron.