(316) Simulation Study of the Competitive Ability of Erect, Semi-erect, and Prostrate Cowpea Genotypes

Ecophysiological simulation models provide a quantitative method to predict the effects of management practices, plant characteristics, and environmental factors on crop and weed growth and competition. The INTERCOM interplant competition model was parameterized, calibrated by monoculture data for three cowpea (Vigna unguiculata) genotypes that differed in growth habit, common sunflower (Helianthus annuus), and common purslane (Portulaca oleracea), and used to simulate competition of cowpea cover crops with sunflower or purslane. The simulation results were compared with observations from field competition experiments in 2003 and 2004. INTERCOM did not simulate biomass production and leaf area index (LAI) of cowpea and purslane well, probably due to a lack of published data on purslane physiology. INTERCOM simulated the competition of cowpea genotypes and sunflower accurately. The simulation model of cowpea and sunflower at two densities was used to study the effects of cowpea growth habits on final biomass production of cowpea and sunflower. The model suggested that the erect growth habit was more competitive than the semi-erect and prostrate growth habits when cowpea genotypes were grown with sunflower. Cowpea leaf area distribution was important to higher cowpea biomass production, while cowpea height growth was important to reduce sunflower biomass.