Submitted to: Journal of Cotton Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 15, 2010
Publication Date: September 1, 2010
Citation: Webster, T.M. 2010. Effect of autumn management on winter annual weeds prior to cotton planting. Journal of Cotton Science. 14:113-118. Interpretive Summary: Conservation tillage (>30% residue) in Georgia has become a common agronomic practice in crop production systems. Benefits of conservation tillage include greater soil moisture and water infiltration and reduced soil erosion, crusting, and sand-blasting of young seedlings associated with wind erosion. While there are many benefits associated with conservation tillage, these systems can be plagued by the occurrence of winter annual weeds at spring crop planting. Primary tillage was used previously, not only to prepare a seedbed for crop planting, but also as an effective means of eliminating existing winter annual weeds. In conservation tillage systems, applications of non-selective herbicides (e.g. glyphosate and paraquat) have replaced primary tillage for cool-season weed control, which is effective for most of the common species, but is often not acceptable for evening-primrose control. Studies were initiated to evaluate the efficacy of post-crop harvest treatments on evening-primrose establishment. Critical establishment of evening-primrose may occur at or around 5 WAH for cotton, while treatments following corn were applied prior to evening-primrose establishment. Application of 2,4-D prior to cotton planting effectively controlled evening-primrose. 2,4-D in both strip-tillage and no-tillage reduced evening-primrose plant density at least 70%. Timely post-crop harvest operations aimed at disrupting the establishment of evening-primrose plants in autumn may also be effective.
Technical Abstract: Field studies evaluated the efficacy of management regimes on control of cutleaf evening-primrose prior to cotton. Different timings and combinations of autumn disking and glyphosate applications were implemented following harvest of the preceding crop. Treatments following corn harvest were inconsistent for annual winter weed control. Treatments that included disking or glyphosate at 5 weeks after harvest (WAH) of cotton had lower evening-primrose ground cover estimates and plant population densities, with the exception of glyphosate applied at 5 WAH in 2004. Critical establishment of evening-primrose may occur at or around 5 WAH for cotton, while treatments following corn were applied prior to evening-primrose establishment. In the second study, pre-plant applications of 2,4-D in three tillage systems were evaluated. Application of 2,4-D effectively controlled evening-primrose. There were differences in the number of evening-primrose plants among both tillage and 2,4-D systems. Conventional tillage had fewer evening-primrose plants than reduced tillages. 2,4-D in both strip-tillage and no-tillage reduced evening-primrose plant density at least 70%. While there was no affect of tillage system on cotton yield, applications of 2,4-D increased cotton growth and yield relative to nontreated controls. 2,4-D was an effective option for evening-primrose control prior to cotton planting. Timely post-crop harvest operations aimed at disrupting the establishment of evening-primrose plants in autumn may also be effective.