Evaluating the Competitiveness and Productivity in a Maize-Bean Intercropping System Using some Indices

Various additive and substitutive series of mixed intercropping of maize (Zea mays L.) with broad bean (Phaseolus vulgaris L.) was compared in a growing season (2007-2008) at the Agricultural Research Field of Ferdowsi University, in Mashhad, Iran. The treatments were sole maize and sole broad bean at their optimum density, and additive and substitutive series of them (%) including 50:50, 50:100, 50:150, 100:50, 100:100, 100:150, 150:50 and 150:100 (maize:bean). A randomized complete block design replicated three times was used. Mixed cropping was significant for grain yields of each crop species. The highest total grain yield, maize yield equivalent (MYE), land equivalent ratio (LER) and system productivity index (SPI) were obtained when maize plants were mixed at a rate of 150% with full and 50% seed rate of broad bean relative to their optimum densities (i.e. 150:50 and 150:100). Also, these treatments were superior in terms of relative crowding coefficient (RCC or K) compared with the others. According to the aggressivity index (A), with increasing the proportion of each component in intercropping, the aggressivity was escalated and dominance occurred. All in all, it is inferred that mixed intercropping of maize with broad bean at a density of more than 150% of the sole maize density (i.e. 150:100) may give better overall yield and income than sole culture of each crop species.