Bactérias promotoras de crescimento vegetal em milho: absorção de nitrogênio, solubilização de fosfato e produção

Abstract

The use of plant growth promoting bacteria (PGPB) in grasses has the potential to optimize the use of nitrogen fertilizers and solubilize phosphate. The consolidation of PGPB use in maize production systems, however, depends on native strains adapted to the growing regions. Thus, the aim of this study was to evaluate the effect of inoculation of regional / local strains on maize growth promotion. A field trial was conducted on maize-grown Vertisol in Passira-PE, Brazil. The experimental design was randomized blocks, with five inoculation treatments, three controls and four replications, totaling 32 experimental plots. Inoculation corresponded to the addition of bacteria: Azospirillum brasilense (AZO); Bacillus sp. (BAC); Pseudomonas spp. (PSE); Stenotrophomonas spp. (STE) and one MIX (BAC + PSE + STE), combined with 50% of the recommended N coverage dose (30 kg ha-1). The witnesses were designated as: TA (absolute witness), who received no inoculation and was not fertilized with N; T50, not inoculated, but fertilized with 50% N in coverage; and T100, which received 100% of N in coverage (60 kg ha-1). Additionally, with the exception of TA, all treatments received N in base (30 kg ha-1 of N). The evaluations were performed in six periods: 15, 20, 36, 50, 70 and 90 days after emergence (DAE). Plant growth and physiology variables, plant growth promotion and ear productivity were evaluated. Inoculation with STE and BAC promoted increments of 10.50 and 13.44% in plant leaf area, respectively. BAC and STE accumulated 276 and 239 kg ha-1 of N, matching the T100. PGPB added and TA native solubilized Ca-bound P in the rhizospheric soil and the nitrogenous controls inhibited solubilization. The AZO, BAC, STE and MIX treatments accounted for 73% of the P content in maize aboveground. BAC and AZO had the best performance of ear yields compared to the T100. The increments were 12.80% (AZO) and 17.58% (BAC). Bacillus sp. and Azospirillum brasilense were the most efficient PGPB for maize culture. The satisfactory performance of Bacillus sp. can be considered in future research, related to the production of bio-inoculants for use in the cultivation of corn in the studied environment.