The effect of N levels, weed control treatments, and their interaction on maize yield and weed growth in sandy soils is not completely understood. Therefore, field experiments were conducted during 2005 and 2006 to determine if management can improve maize competitiveness with weeds, and thus achieve the yield potential of maize in sandy soils. The experiment included three N levels (300, 338, and 375 kg/ha) and five weed control treatments, e.g., hand hoeing twice, hand hoeing three times, fluroxypr hoeing once, hoeing once bispyribac-Na, and a nonweeded check. N rates affected dry weight of weeds growing with maize except with large crabgrass. Biomass of common purslane, considered a nitrophilous species, was increased by all N levels. Weeds were controlled by all treatments compared with the nontreated check; however, herbicide treatments were not superior to hand-hoeing treatments. Using more N favored growth and yield of maize more than weeds. Adding N fertilizer also improved most yield parameters. Highest grain yield of maize resulted at 375 kg/ha N. All weed control treatments improved grain yield two- to threefold compared with the nonweeded check. The interaction between N rates and weed control treatments had significant effects on dry biomass of common purslane and barnyardgrass, as well as grain index and biological yield parameters of maize. Grain yields were improved with fluroxypyr applied 2 wk after sowing (WAS) maize followed by one hand hoeing 6 WAS or hoeing at 3 WAS followed by bispyribac-Na applied 6 WAS. However, highest yields were obtained by hoeing early during the growing season.
Nomenclature: Maize, Zea mays L; fluroxypyr; bispyribac-Na; common purslane, Portulaca oleracea L; barnyardgrass, Echinochloa crus-galli (L.) Beauv; large crabgrass, Digitaria sanguinalis (L.) Scop.