Crop canopy architecture is known to affect weed performance. Field experiments were conducted to examine the effect of altered crop canopy architecture and light interception on growth and development of wild proso millet and giant foxtail, two problematic weed species. Crop canopy architecture was manipulated by planting two sweet corn varieties contrasting in canopy architecture (Bonus-has a dense leaf canopy and Sprint-has an open leaf canopy) at two row spacings (51-cm and 76-cm rows). Results showed that sweet corn variety, rather than row spacing, altered crop canopy architecture, which in turn altered photosynthetically active radiation (PAR) and red:far-red light ratio (R:FR) received by both weeds. The competitive Bonus canopy had a higher (P<0.05) PAR and R:FR than Sprint at anthesis and harvest. Bonus also more effectively suppressed weed growth and development than Sprint, and weeds growing on Bonus plots had reduced tiller numbers, reduced biomass, lower population densities, and reduced seed production (P<0.05). These responses were attributed to the Bonus canopy having a higher canopy area index, which intercepted more light resulting in lower PAR and R:FR received by both weeds. This study suggests that crop variety selection is an important consideration for weed suppression in row-cropping systems.
Key words: Crop canopy architecture, light interception, photosynthetically active radiation, red:far-red ratio, row spacing, sweet corn, wild proso millet, giant foxtail.
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