COMPETITIVE ABILITIES OF 6 CORN (ZEA-MAYS L) HYBRIDS WITH 4 WEED-CONTROL PRACTICES

Six corn hybrids were studied in field experiments in 1989 and 1990 to identify hybrids and corn plant characteristics that may be valuable in systems using reduced levels of weed control. Four weed control tre atments (no-control, cultivation-only, band herbicide-plus-cultivation , and broadcast herbicide) represented main plots and maize hybrids we re subplots. Medium-season hybrids with differences in height, early-s eason vigor, and leafiness were used. There were significant differenc es among hybrids in leaf angle, leaf width, leaf number, plant height, leaf area index (LAI), plant dry matter (DM) and grain and stover yie lds. Lower yielding hybrids had grain yields that ranged from 87 to 91 % of the highest yielding hybrid. Aboveground com characteristics wer e not correlated with weed numbers, weed cover, or weed biomass. A sig nificant interaction between hybrid and weed control for grain yields was observed in 1989, suggesting that some hybrids are more competitiv e when weed pressure is high.