Inoculation of Brachiaria spp. with the plant growth-promoting bacterium Azospirillum brasilense: An environment-friendly component in the reclamation of degraded pastures in the tropics

Estimates are that in Brazil there are about 180 million hectares of pasturelands, 70% with some degree of degradation. Reclamation of such areas demands re-establishment of soil fertility, plant growth and forage production, and microbial inoculants might help in these processes. We evaluated the ability of two strains of Azospirillum brasilense to promote the growth of two genotypes of Brachiaria spp. (=Urochloa spp.). The experiments were set up at three different sites in Brazil, and forage production estimated for 26 cuts in two years. On average, increases of 5.4% and 22.1% in response to N-fertilizer alone and to N-fertilizer in combination with Azospirillum, respectively, were observed over the non-inoculated and non-N-fertilized control treatment. Increase in N accumulation in the biomass in response to Azospirillum was equivalent to a second application of 40 kg of N-fertilizer ha−1. Estimates attributed to the inoculation were of gains of 0.103 Mg C ha−1, corresponding to 0.309 Mg CO2-eq ha−1. Inoculation with Azospirillum may represent a key component of programs to reclaim degraded pastures and help sequestration of CO2 from the atmosphere.