EFFECT OF PLANTING PATTERNS AND INTER-ROW CULTIVATION ON COMPETITION BETWEEN CORN (ZEA-MAYS) AND LATE EMERGING WEEDS

Narrower corn row widths, higher crop densities, and interrow cultivat ion may be used as part of integrated weed management (IWM). During a three-year study, we tested whether these factors affected corn growth , development and grain yield at final harvest, and weed biomass when weeds were late-emerging (after the three-leaf stage of corn). Increas ing corn density from 7 to 10 plants m(-2) or decreasing row width fro m 75 to 50 cm significantly increased corn leaf area index (LAI), and reduced photosynthetic photon nux density (PPFD) available for a mixtu re of weed species located below the corn canopy. Narrower rows and hi gher corn density significantly reduced biomass of late-emerging weeds . Corn yields increased significantly (10 to 15%) only when narrower r ows were used. Intraspecific competition between corn plants in the hi gher density significantly reduced early corn growth and offset any ga in in yield from reduced weed competition. In comparison to plots wher e late-emerging weeds grew uncontrolled, inter-row cultivation did not decrease biomass of late-emerging weeds, hence did not increase corn yield. We recommend using narrower row widths to reduce weed competiti on and increase corn yield. Increased corn densities had no net yield benefit. Early-season weed management is crucial as the later-emerging weeds were less important in terms of their effect on yield.