Interactions of bush bean intercropped with field and sweet maize

Common bean, Phaseolus vulgaris L., is traditionally intercropped with maize by small-scale farmers in northwest Spain. Interactions of genotypes or beans with cropping systems and seasons were studied to determine if selection of bean in sole cropping would be a valid approach to genetic improvement for intercropping. In this experiment, 10 dry bush bean varieties were evaluated in sole cropping and intercropping with two types of maize (field and sweet maize) at two locations for 2 years. The performance of bean genotypes in each cropping system was compared with respect to developmental plant characteristics, seed yield and yield components and rood quality traits. A significant bean genotype x cropping system interaction was found for period of flowering and seed yield, and there were significant differences between cropping systems for pods per plant, seed length and seed coat proportion. Intercropping with field maize reduced bean yield by 55%, and intercropping with sweet maize reduced bean yield by 44%. Significant and high correlations of bean yields were obtained between sole cropping and intercropping with maize. Mean yields were used to calculate the land equivalent ratios (LERs), which averaged 1. 12 for intercropping with field maize and 0.93 for intercropping with sweet maize. Specific variety combinations reached LER values greater than one. Net income was higher for some intercrop patterns than for bush bean sole crop. The most competitive bean varieties yielded the most when intercropped with maize but those varieties were not necessarily the highest yielding in sole cropping. The most competitive bean varieties were the latest to flower. The evaluation of bush bean genotypes for agronomic and food quality traits under sole cropping provides sufficient information to select varieties efficiently for the field maize-bean and sweet maize-bean intercropping systems. Greatest net income was realized when bush beans intercropped with sweet maize, provided a system with higher added value compared to intercropping with field maize. (C) 2001 Elsevier Science B.V. All rights reserved.