Inoculação e coinoculação bacteriana em feijão-caupi sob salinidade: efeitos na nodulação, crescimento, fisiologia e produção.

Abstract

The cowpea crop has great socioeconomic importance for the Brazilian Northeast, but in this region, its production is reduced by water scarcity and, whwn irrigated, by the salinity of the water, and availability of nitrogen to the plant, making it necessary to use of cultivation strategies, such as the co-inoculation of diazotrophic bacteria and growth-promoting bacteria in plants, favoring na increase in biological nitrogen fixation (BNF). Thus, the objective of this work was to evaluate the efficiency of inoculation ans co-inoculation with Bradyrhizobium ssp. and Azospirillum brasilense in cowpea under salinity. The experiment was carried out in a greenhouse on campus I of the Federal University of Campina Grande. The treatments consisted of T1 (without mineral N fertilizer and without inoculant); T2 (fertilized with mineral N and without inoculant); T3 (Bradyrhizobium ssp. inoculation) and T4 (Bradyrhizobium ssp. and Azospirillum brasilense co-inoculation) submitted to saline levels of 0.4; 1.9; 3.4; 4.9 and 6.4 dS.m-1. The experimental arrangement was in randomized blocks, in a 4x5 factorial scheme with five replications, totaling 100 experimental units. Aspects of growth, production, physiology and nodulation were evaluated. The variables were submitted to analysis of variance through the statistical software SISVAR and the level of significance by the Tukey test of means (p < 0.05) for the data obtained in the different treatments of qualitative nature, while the data of a quantitative nature were submitted to the regression study. At the threshold salinity level of cowpea, 3.4 dS.m-1, inoculation resulted in higher production. The increase in the electrical conductivity of irrigation water negatively affected the nodulation, growth, physiology and production of cowpea of the <corujinha= variety.