Cowpea Root Growth under Water Availability and Co-inoculation with Growth Promoting Rhizobacteria

Abstract

ABSTRACT Rainfall variations can occur with crops in field condition which can result in soil water restrictions and impair crop development. Inoculation with Azospirillum genus bacteria can be presented as an alternative, as it has the ability to fix N2, promote root growth and produce beneficial metabolites to plants under water stress conditions. Thus, the objective was to co-inoculate A. brasilense and Bradyrhizobium sp. in cowpea and verify the potential to minimizing the effects caused due to water availability on root growth and nodulation. The study was carried out in a greenhouse with completely randomized block design and 4 replications in 4 × 4 factorial arrangement, the treatments being: (i) non-inoculated, (ii) N-fertilizer, (iii) inoculated with Bradyrhizobium sp. and (iv) co-inoculated with Bradyrhizobium sp. + A. brasilense. All treatments were associated with soil water tension of 15, 30, 45 and 60 kPa. Co-inoculation increased dry mass and nodules number. The root surface area and dry mass of cowpea roots showed an increase from the 50.55 kPa tension with co-inoculation.