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Combining empirical research with simulation modeling may improve our understanding of the dynamics of crop:weed competition and for testing hypotheses on the importance of specific traits for enhancing crop performance in mixtures. Two field experiments were conducted to quantify and compare estimates of traits important for radiation interception and utilization in four maize hybrids and Abutilon theophrasti grown in monoculture. Early leaf area growth rate did not vary among maize hybrids within a year, but varied among years. The response of CO2 assimilation rate to absorbed radiation and leaf nitrogen content did not differ among hybrids. Abutilon theophrasti and two old maize hybrids partitioned more new biomass to stem relative to reproductive organs than newer hybrids. Old hybrids had greater specific leaf area during the period of most rapid growth, grew taller, and leaf area was distributed higher in their canopy. Extinction coefficients for diffuse radiation did not differ among hybrids or between years. Results suggest that these four maize hybrids may differ in their ability to intercept incident radiation, which may influence their ability to compete for light.