Performance variation among improved common bean (Phaseolus vulgaris L.) genotypes under sole and intercropping with maize (Zea mays L.)

摘要

Periodic assessment of released common bean cultivars is essential to screen genotypes that offer superior intercropping advantage to farmers when grown in association with maize. Thus, comparative performance of improved genotypes representing commonly used growth habit and market classes were investigated under sole and intercropping system at Halaba special district, Southern Ethiopia. Treatments consisted of a factorial combination of seven common bean genotypes and two cropping systems, which were arranged in a split plot design replicated three times. Cropping system and genotype were assigned as main and sub plot factors, respectively. Cropping system by genotype interaction was significant for bean grain yield and two of the yield components causing moderate changes in ranking. Relative yield reduction due to association with maize varied from 26% for genotype Sari-1 (Type II) to 67% for Awash Melka (Type III), while maize suffered a smaller reduction, 7%. The total Land Equivalent Ratio (LER) values under intercropping with maize ranged from 1.34 for the improved Hawassa Dume (Type II) to 1.01 for the local cultivar, Red Wolayita (Type III). Genotypes with greater LER were not necessarily all top yielders under sole cropping, because of the genotype by cropping system interaction. Bush and semi bush (Type I and II) types produced the highest intercropping advantage, as a group. The two export bean types, which have a semi climbing (Type III) growth pattern, had the lowest LER values among the improved genotypes. Genotypes such as Hawassa Dume and Sari-1 are preferred to the conventionally used cultivars for maximizing intercropping advantage. Developing bush type export genotypes may help broaden their expansion outside their traditional zones since better performance under intercropping could attract more farmers to adopt them.