Abstract

Field experiments were conducted in 2006 and 2007 to evaluate the competitive ability of bush typered kidneybean (RKB) (Phaseolus vulgaris L.) cultivars against redroot pigweed (Amaranthus retroflexusL.). Three cultivars of RKB (Akhtar, Sayyad and D81083) and five A. retroflexus densities (0, 4, 8, 16 and32 plants m−2) were established in a factorial arrangement. A. retroflexus had a greater plant height andgrowth rate (GR) but a lower leaf area index (LAI) than RKB cultivars in almost all treatments. Higherdensities of A. retroflexus increased LAI and GR but decreased yield of RKB cultivars. The cv. Sayyad andD81083 had the greatest and lowest LAI and GR, respectively, in competition with A. retroflexus. Themaximum intercepted photosynthetically active radiation (PAR) at noon by A. retroflexus was 90.4 and66.0% in competition with cv. D81083 and Sayyad, respectively. The seed yield and pod number per plantof RKB cultivars decreased severely with increasing A. retroflexus density. A. retroflexus seed number m−2was the highest and lowest in competition with cv. D81083 and Sayyad, respectively. The competitiveability of RKB cultivars was compared using parameters estimated through two-parameter yield loss-relative leaf area model. The relative ranking of the RKB cultivars examined for their competitiveness,supported by modeling results, was Sayyad > Akhtar > D81083.