Crop Density, Sowing Pattern, and Nitrogen Fertilization Effects on Weed Suppression and Yield In Spring Wheat

Abstract

Abstract Recent studies have shown major advantages of increased crop density and spatial uniformity for competition of wheat with weeds. Field experiments were performed over 3 yr to determine whether the effects of crop density and sowing pattern on weed suppression are influenced by nitrogen fertilization. The independent variables were crop sowing pattern (normal rows and a highly uniform pattern), seeding density (204, 449, and 721 seed m−2) and nitrogen fertilization (0 and 80 kg nitrogen ha−1) of spring wheat, grown under high weed pressure. Increased crop density had strong and consistent negative effects on weed biomass and positive effects on crop biomass and yield. At the highest crop density, weed biomass was less than half that at the lowest density. Weed biomass was generally lower, and yield higher, in the uniform pattern, except in one case in which a combination of factors gave one weed species an early size advantage over the crop. When weeds were controlled with herbicide, no effects of...