Maize Genotype by Cropping Pattern Interactions: Monoculture vs. Intercropping1

Abstract

Breeding programs to develop new crop cultivars for small farm cropping systems must consider the range of intercrop patterns in which these cultivars will be used. Most research in the past has concentrated on selection for monoculture. The objective of this study was to evaluate cultivar by cropping pattern interactions in a set of maize (Zea mays L.) genotypes currently used by the international research centers and the Colombian national maize program. In three consecutive years at the Centro Internacional de Agriculture Tropical station (1,000 m elevation, 47 N Lat.), maize cultivars were planted at optimum densities for monoculture and intercropping with two types of bean (Phaseolus vulgaris L.): a determine bush type and anindeterminate climber type. Optimum production conditions were attempted using irrigation and pesticides where needed. Average monoculture maize yields were about 5,000 kg/ha, with some cultivars producing up to 7,600 kg/ha. Intercropping with bush beans reduced maize yields in one year out of three. Intercropping with the more competitive climbing bean reduced maize yields in all 3 years. Significant yield differences among maize cultivars were found in all 3 cropping patterns each year. The cropping pattern by maize cultivar interaction was not significant for maize yields, however for bean yields there were differences among intercropped maize cultivars and a cultivar by cropping pattern interaction in the second and third years. Highly significant (P<0.01) correlations of maize yields between cropping patterns (r = 0.78 to 0.91) in second and third year data suggest consistency of results from one system to another. The significant difference in bean yields among maize cultivars emphasizes the importance of evaluating cropping patterns in terms of total production or income from both crops before making decisions on the best maize cultivar to recommend for intercropping.