Evaluation of herbicide programs in no-till and conventional tillage corn.

ABSTRACT Experiments were conducted with corn at two sites in 2003 to compare glyphosate-based herbicide programs to conventional herbicide programs in conventional and no-till tillage systems. Herbicide treatments included: s-metolachlor plus atrazine preemergence (PRE) or no PRE; postemergence (POST) herbicide treatments were nicosulfuron plus rimsulfuron plus dicamba, glyphosate alone or with atrazine, and no POST herbicide; and postemergencedirected (PDIR) treatments included glyphosate, ametryn, or no PDIR herbicide. Entireleaf morningglory, ivyleaf morningglory, pitted morningglory, and tall morningglory where controlled 93% or greater 2 wk after POST herbicide application (WAP) with all treatments including POST herbicides. By 2 wk after PDIR herbicide treatment (WAPD), control was higher when a PDIR herbicides were applied. Broadleaf signalgrass, fall panicum, large crabgrass, and sicklepod were controlled 96% or greater 2 WAP with all treatments receiving a POST herbicide application. However, in the absence of a PDIR herbicide application, control was lower 2 WAPD. Palmer amaranth and common ragweed were controlled 99% or greater in the no-till tillage system by both herbicide programs, however in the conventional tillage system control was reduced with the conventional herbicide program compared to the glyphosate system. Smooth pigweed was controlled completely by both herbicide programs regardless of the tillage system used. Corn yield in the conventional tillage system was 1010 kg/ha higher than in the no-till. Net returns varied according to grain yield, which varied between tillage systems.