Dry Matter Production and Distribution of Bean Cultivars under Weed Competition

This study aimed to determine the competitive ability of three bean cultivars and six weed species and to quantify the effect of competition on the plants' growth and dry mass allocation. A factorial scheme 3 x 6 + 9 was adopted, consisting of a combination of three genotypes (Colibri IPR, IPR Eldorado, Pearl) in competition with six species of weeds (Euphorbia heterophylla, Bidens pilosa, Cenchrus echinatus, Amaranthus spinosus, Commelina benghalensis and Brachiaria plantaginea), plus nine additional treatments corresponding to the bean cultivars and weeds without competition. Both treatments were arranged in a randomized block design with four replicates, with each pot (containing 5 dm(3) soil) representing an experimental unit. The period of coexistence between the bean cultivars and weeds was 45 days after emergence, followed by collection of the plant material to assess the dry mass distribution among the different organs (roots, leaves and stems). The bean cultivars had a lower biomass accumulation when in competition with the weed species. The root was the main organ affected negatively. Conversely, the leaves and the stems of the competing species, in general, were the most affected. Overall, the cultivar Pearl was the genotype most tolerant to weed competition and E. heterophylla was the least competitive weed. A. spinosus and B. plantaginea were found to have a greater capacity to compete with the bean crop.