YIELD OF COMMON BEAN (Phaseolus vulgaris L.) IN RELATION TO SUBSTRATE VERMICOMPOST CONCENTRATION AND WATER DEFICIT

The beneficial effect of vermicompost on yield of some cultivars has been documented, but there is little information about its effect when it is combined with stress-inducing factors. The objective of this study was to evaluate the combined effect of vermicompost and water stress on bean (Phaseolus vulgaris L.) yield with the hypothesis that vermicompost modifies the soil-plant system and diminishes the effect of water deficit. In greenhouse, the yield of two common bean cultivars (drought-susceptible and tolerant to drought) was assessed in soil with or without 1.5 % and 3 % of vermicompost, with irrigation in the complete cycle and its suspension, starting from flowering. The experimental design was completely randomized with factorial arrangement and five replications. Production of inflorescence, pods, and seeds were evaluated. Under both conditions of irrigation and cultivars, the addition of 3 % of vermicompost increased the total of inflorescence by 31 %, the number of produced pods by 36 %, 16 % that of harvested pods, 34 % in number of seeds and 33 % in seed biomass (yield) per plant. Negative effect of suspending irrigation was observed on the number of pods and seeds and on seed yield; however, with 3 % of vermicompost susceptible and tolerant cultivar increased the number of pods by 17 and 15 %, as well as the amount of seeds by 28 and 48 %, and seed yield by 15 and 50 %. Interactions between factors showed different reaction of cultivars to water stress, vermicompost, and their combination. It was observed that vermicompost in substrate modifies the soil-plant system and diminishes the negative reaction of common bean crops to water stress, since it significantly increases their yield.