Influence of Herbicide Application Timing on Corn Production in a Hairy Vetch Cover Crop

Abstract

The time of killing a hairy vetch (Vicia villosa Roth) cover crop relative to planting no- tillage corn (Zea mays L.) is critical to optimizing the benefits derived from the cover crop mulch. Research was conducted to determine the optimum timing for herbicide application to control hairy vetch for no-tillage corn production. Herbicides were applied 1 to 3 wk before planting corn (preplant), immediately after planting corn (preemergence), or after corn emergence (postemergence). Herbicide plots were split by N sidedressing at 0 or 80 lb/acre. Biomass of hairy vetch increased by an average of 1620 lb/acre and N content increased by an average of 44 lb/acre between the preplant and preemergence application dates but little change occurred between the preemergence and postemergence application dates. Despite this N increase between herbicide applications, herbicide application date had no effect on corn response to sidedressed N. Soil texture did appear to influence corn response to sidedressed N; corn yield was higher when N was sidedressed in two experiments on coarse-textured soils but was not influenced by sidedressing in two experiments on fine-textured soils. Yield was higher when corn was grown with the preplant herbicide program than the preemergence herbicide program in one of four experiments and higher when corn was grown with the preplant herbicide program than the postemergence herbicide program in three of four experiments. Results indicate that optimum yield of corn grown in a hairy vetch cover crop requires killing vetch before planting but sidedressing with N may only be necessary on coarse-textured soils.