Unraveling the potential: assessment of the effect of Azospirillum brasilense inoculated via seeds on the growth and production of Mombaça grass

Abstract

Nitrogen fertilization in pastures is considered one of the primary limiting factors that significantly enhance forage biomass production. Traditional chemical fertilizers used in crop cultivation are derived from petrochemical and mining industries. These production chains have undergone continuous and consistent structural changes year after year, affecting the prices of these inputs for farmers, consequently escalating production costs and even rendering investment in livestock farming unfeasible. For this reason, research becomes crucial to evaluate alternative techniques that can complement or fulfill the nitrogen demand in forage crops. The bacterium Azospirillum brasilense has emerged as a viable alternative to reduce costs in pasture establishment and maintenance, serving as a nitrogen source when compared to traditional sources. The objective of this study was to assess the effect of Azospirillum brasilense inoculation on the growth and production of Panicum maximum cv. Mombaça. The experimental design employed was a randomized complete block design with four treatments and four replications. Each plot consisted of three plants, resulting in a total of 48 experimental units. The treatments comprised: T1 - natural soil (NS), T2 - Azospirillum brasilense (BAC.), T3 - nitrogen topdressing (N), T4 - Azospirillum brasilense and nitrogen topdressing (BAC+N). Evaluations were conducted at 60 and 90 days after sowing (DAS), assessing the following variables: plant height (PH), number of leaves (NL), number of tillers (NT), aboveground green biomass (AGGB), aboveground dry biomass (ADBB), root fresh biomass (RFB), and root dry biomass (RDB). Significant effects (P<0.05) were observed for inoculation and nitrogen topdressing on the assessed traits: plant height, number of leaves, number of tillers, aboveground green biomass, aboveground dry biomass, root fresh biomass, and root dry biomass. Notably, nitrogen topdressing either solely or in combination with seed inoculation of the forage yielded positive outcomes for all studied variables at both 60 and 90 DAS. A favorable impact on the development of Mombaça grass was evident across all parameters studied in samples receiving nitrogen topdressing and Azospirillum spp. inoculation.