|Koger Iii, Clifford|
Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/26/2003
Publication Date: 7/1/2004
Citation: Reddy, K.N., Koger III, C.H. 2004. Live and killed hairy vetch cover crop effects on weeds and yield in glyphosate-resistant corn (zea mays). Weed Technology 18:835-840. Interpretive Summary: Weed suppression effects of cover crop residue decrease with time following cover crop desiccation at crop planting. Planting corn into live hairy vetch could potentially extend period of weed suppression. Information is lacking on integration of live hairy vetch cover crop and glyphosate postemergence applications in glyphosate-resistant corn. Scientists at the Southern Weed Science Research Unit in Stoneville, Mississippi completed a 2-yr study evaluating the effects of killed, live, and band killed hairy vetch cover crop with glyphosate applications on weeds and yield. Leaving hairy vetch alive up to 3 weeks after planting corn increased hairy vetch biomass by 1,520 to 2,020 kg/ha compared with a kill at corn planting. This additional hairy vetch biomass did suppress certain weed species and reduce total weed dry biomass. However, these benefits did not translate in to increased corn yield as corn grown in killed hairy vetch yielded more than corn grown in live hairy vetch. These findings indicate that hairy vetch killed at corn planting has the potential for reducing density of certain weed species in glyphosate-resistant corn production systems; however, optimum weed control and higher yield was obtained when glyphosate was used. In a hairy vetch-based corn production system, weeds can be managed with a glyphosate-only program and potentially eliminate the need for prophylactic preemergent herbicides and also derive environmental benefits.
Technical Abstract: A 2-yr field study was conducted during 2002-2003 on a Dundee silt loam soil at the Southern Weed Science Research Unit farm, Stoneville, MS, to examine the effects of hairy vetch cover crop (HV-K, hairy vetch killed at corn planting; HV-B, hairy vetch killed in a 38-cm band over crop row at corn planting; HV-L, hairy vetch live; and no hairy vetch) and glyphosate POST (broadcast, banded, and no herbicide) application on weed control and yield in glyphosate-resistant corn. Two applications of glyphosate at 0.84 kg ae/ha were applied 3 and 5 weeks after planting (WAP) corn, respectively. Hairy vetch dry biomass was higher in HV-L (4,420 kg/ha) and HV-B (4,180 kg/ha) than in HV-K (1,960 kg/ha) plots at 7 WAP. Hairy vetch reduced densities of pitted morningglory, prickly sida, and yellow nutsedge in HV-B and HV-L compared with HV-K or no hairy vetch plots, but hairy vetch had no effect on densities of barnyardgrass, johnsongrass or large crabgrass regardless of desiccation type at 7 WAP. Total weed dry biomass at 7 WAP was lower in HV-B and HV-L than in HV-K and no hairy vetch plots. Corn yield was higher in HV-K (10,280 kg/ha) than HV-B (9,440 kg/ha) and HV-L (9,100 kg/ha), and yields were similar between HV-K and no hairy vetch (9,960 kg/ha). Glyphosate applied broadcast produced highest yield (11,300 kg/ha) compared with banded application (10,160 kg/ha). These findings indicate that hairy vetch cover crop has potential for reducing density of certain weed species in glyphosate-resistant corn production systems; however, optimum weed control and higher yield was obtained when glyphosate was used.