A 2-yr field study was conducted from 2002 to 2003 on a Dundee silt loam soil at the Southern Weed Science Research Unit Farm, Stoneville, MS (33°26′N latitude), to examine the effects of hairy vetch cover crop (hairy vetch killed at corn planting [HV-K], hairy vetch killed in a 38-cm-wide band centered over the crop row at corn planting [HV-B], hairy vetch left alive [HV-L], and no hairy vetch [NHV]) and glyphosate postemergence (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 wk after planting (WAP) corn. 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 NHV plots, but hairy vetch had no effect on densities of barnyardgrass, johnsongrass, and large crabgrass at 7 WAP regardless of desiccation. Total weed dry biomass at 7 WAP was lower in HV-B and HV-L than in HV-K and NHV plots. Corn yield was higher in HV-K (10,280 kg/ha) than in HV-B (9,440 kg/ha) and HV-L (9,100 kg/ha), and yields were similar between HV-K and NHV (9,960 kg/ha). Glyphosate applied broadcast resulted in the highest corn yield (11,300 kg/ha) compared with a banded application (10,160 kg/ha). These findings indicate that hairy vetch cover crop has the potential for reducing the density of certain weed species in glyphosate-resistant corn production systems; however, optimum weed control and higher yield were obtained when glyphosate was used.
Nomenclature: Glyphosate; barnyardgrass, Echinochloa crus-galli (L.) Beauv. #3 ECHCG; hairy vetch, Vicia villosa Roth # VICVI; johnsongrass, Sorghum halepense (L.) Pers. # SORHA; large crabgrass, Digitaria sanguinalis (L.) Scop # DIGSA; pitted morningglory, Ipomoea lacunosa L. # IPOLA; prickly sida, Sida spinosa L. # SIDSP; yellow nutsedge, Cyperus esculentus L. # CYPES; corn, Zea mays L. ‘AG RX 738RR’, ‘DKC 69-72RR’.
Additional index words: Cover crop, glyphosate, integrated weed management, mulch, transgenic corn, weed biomass, weed density.
Abbreviations: HV-B, hairy vetch killed in a 38-cm-wide band centered over the crop row at corn planting; HV-K, hairy vetch killed at corn planting; HV-L, hairy vetch left alive; NHV, no hairy vetch; POST, postemergence; WAP, weeks after planting.