Review of 2008 by Region - Southeast

Residual Effect of Primary Tillage on Weed Control and Cotton Yield
C. D. Monks¹, M. G. Patterson², and A. Price^3
1,2Ala. Coop. Ext. System, Auburn University, and ³USDA-ARS

Abstract

A field trial was initiated (2006) to evaluate the effect of at-plant soil preparation, PRE, and POST programs on weed control and cotton yield; and to determine residual effect in subsequent years.  Cotton was planted in a completely randomized experimental design with a 4 X 3 X 2 factorial arrangement of treatments, with at-plant PREP (main plots), PRE herbicide systems (sub-plots), and POST herbicide treatments (sub-sub plots).  At-plant PREP treatments included:  inversion fb disking with pendimethalin PPI; two diskings with pendimethalin PPI; no-tillage with pendimethalin PRE, and no-tillage alone.  PRE treatments included: fluometuron PRE, prometryn PRE, and no PRE. POST treatments included:  glyphosate POST and no POST.   Following initiation in 2006, the trial was planted no-till in 2007 and 2008 using pendimethalin PRE.  After three years, glyphosate-susceptible redroot pigweed populations were significantly reduced when glyphosate was applied POST regardless of the PRE program.  Susceptible pigweed populations were lowest for the no-till/pendimethalin PRE/glyphosate POST program and yield was comparable to the inversion, disk/pendimethalin PPI/glyphosate program.  When no POST glyphosate treatment was applied, population was highest and yield lowest in the no-till plots.  Given the reproductive potential of pigweed, surviving glyphosate-resistant plants in producer's fields would likely continue to infest affected fields.  Further research is required to determine the utility of tillage for herbicide resistance management.