Simbiose de bactérias fixadoras de nitrogênio com feijoeiro-comum em diferentes valores de pH

Abstract

The objective of this study was to evaluate the effect of the culture medium pH in the symbiotic effectiveness of Rhizobium strains in soil, with and without liming. Assays were performed in greenhouse, with and without liming, and in the field, with liming. The experimental design was randomized blocks with four replicates, and treatments were five strains (UFLA 02-100, UFLA 02-68, UFLA 04-195, UFLA 04-202 and CIAT 899), grown in a 79 culture medium with different pH values (5.0, 6.0 and 6.9), and two controls without inoculation: with or without mineral nitrogen. Variables analyzed were number and weight of dry nodules, shoot dry matter, relative efficiency, nitrogen content and accumulation in shoots and grains, number of pods per plant, number of grains per pod, and yield and weight of 100 grains. The optimum pH value for the culture medium varied with the strains and the variable analyzed. Treatments with liming were superior to the others. In the field, regardless of the inoculant pH, the native soil populations and the introduced strains promoted grain yields similar to those of the control with 70 kg ha-1 of N and to those of the reference strain CIAT 899.