Yield, yield components and nutrients uptake in Zuri Guinea grass inoculated with plant growth-promoting bacteria

Abstract

The objective of this study was to evaluate the effects of strains of Azospirillum brasilense, Pseudomonas fluorescens and Rhizobium tropici on biomass yield and nutrients uptake of shoots and roots of Megathyrsus (syn. Panicum) maximus cultivar BRS Zuri (Zuri Guinea grass) inoculated with plant growth-promoting bacteria (PGPB). Treatments consisted of inoculation and re-inoculation with A. brasilense strains Ab-V5 and Ab-V6, P. fluorescens strain CCTB 03 and of co-inoculation with R. tropici strain CIAT 899 + A. brasilense Ab-V6, with or without N-fertilizer (100 mg dm^-3). Evaluations were performed on three cuts for the determination of root and shoot dry weight yield, morphological compositions, tiller mass, number of tillers, and nutrient uptake. Inoculation with bacteria in association with N-fertilizer increased N, NH₄⁺, Ca, Fe, Mn and Zn accumulation in shoots and P and K uptake in roots. P. fluorescens and co-inoculation with R. tropici CIAT 899 + A. brasilense Ab-V6 increased the relative chlorophyll index in relation to the non-inoculated control. As expected, PGPB were not able to fully replace N-fertilization. However, when combined with N-fertilizer, the PGPB increased yield, the relative chlorophyll index, and the uptake of N, NH₄⁺, Ca, Zn, Mn and Fe of Zuri Guinea grass. The results indicate that PGPB can represent a sustainable alternative for reducing the use of N-fertilizers. There were no effects of re-inoculation with PGPB on the nutrition or yield of Zuri Guinea grass, demonstrating that the determination of the method of application and periodicity of inoculation still require investigation.