Eficiência da simbiose de bactérias fixadoras de nitrogênio com feijoeiro comum em diferentes condições de pH

Abstract

The common bean, besides being an excellent source of protein for the population and be economically important is able to form symbioses with nitrogen-fixing bacteria. Thus, it can replace all or part of the nitrogen fertilizer use, reducing production costs and pollution of soil and water. The soil acidity is one of the main factors that may affect the symbiosis. However it, can induce a pre-adaptation to acidic conditions when the bacteria is exposed previously to a slightly acid pH. Thus, the objective this research was to verify if the cultivation of strains of Rhizobium (UFLA02-100, UFLA02-68, UFLA04-195, UFLA04-202 e CIAT899) in media with different pH conditions (5,0; 6,0 and 6,9) promotes changes in symbiotic efficiency, seeking to optimize the production of inoculants, and also to verify the efficiency of these strains in biological nitrogen fixation and competitiveness with native populations. Two experiments were carried out in a greenhouse and one in the field. The ideal pH value for preparation of the inoculum varied with the strains tested, and the variable analyzed. However, all variables except the relative efficiency were higher in treatments with liming. In the field trial, the native populations of soil and inoculation with strains promoted grain yield similar to the control with 70 kg.ha-1 of N and the reference strain CIAT 899.