Palmer Amaranth Control in Three Cotton Tillage Systems

Recent advances in herbicide technology and genetically modified cotton have increased the adoption of conservation tillage in the Texas High Plains.  Research to determine effective and economical weed management in conservation tillage systems was conducted in 2007-09 at the Texas AgriLife Research Center near Halfway using center pivot irrigation.  Glyphosate-tolerant cotton followed corn in 2007 and grain sorghum in 2008 and 2009.  Treatments compared glyphosate alone to glyphosate plus preemergence and postemergence herbicides that included pendimethalin, prometryn, pyrithiobac and diuron.  Tillage systems were conventional-till, no-till and strip-till.  In 2007, effective Palmer amaranth (Amaranthus palmeri) control was achieved with all treatments in the strip-tillage system.  Similar Palmer amaranth weed control was observed with all treatments in the strip-tillage system two weeks after the first POST application, four weeks after the layby treatments and among tillage systems in 2008.  When averaged across herbicide treatments, the conventional-till and strip-till systems produced greater yield than the no-till systems in 2007.  In 2008, greater yields were produced in the strip-till plots compared to conventional-till and no-till.  Gross returns based on cotton lint yield and herbicide input costs were used to determine economics of herbicide treatments in each tillage system.