Avaliação do potencial de bactérias do solo na solubilização de potássio a partir de fonolito

Abstract

Potassium-solubilizing microorganisms have been used as bioinoculants to promote the growth of different crop species. Our study aimed to isolate, characterize, and test potassium-solubilizing bacteria from potassium rocks. The bacteria were isolated from tomato rhizosphere soil and a coastal rock formation in the state of Espírito Santo. Dilutions of 10⁻¹ to 10⁻⁹ were made and these were inoculated on plates using Aleksandrov and B & B culture media supplemented with phonolite-type potassium rock. Additionally, bacteria from the Johanna Döbereiner Resource Center were used as a source of potential solubilizing microorganisms. Organisms positive for K solubilization were grown in pure culture using DYGS medium and identified through analysis of the 16S rRNA gene sequences. Among the positive genera for solubilization are: Burkholderia, Paraburkholderia, Enterobacter, Ralstonia, Microbacterium, Nguyenibacter, Rhizobium, Bacillus, and Arvibacter. The BR 11366 strain of Paraburkholderia tropica and two isolates of Rhizobium sp. stood out in the liquid solubilization test. Unlike Rhizobium, the other microorganisms did not acidify the culture medium, indicating the action of a possible different mechanism for K solubilization. Inoculation with the different bacteria provided a greater accumulation of dry matter in the shoot of millet when cultivated at a low dose of K (40 kg ha⁻¹). The performance of plants inoculated under this condition was similar to that of plants under a high dose of K (400 kg ha⁻¹). Strains NZ11, from Arvibacter sp., and BR 3487, from P. tuberum, stood out as the best plant growth promoters. We conclude that the evaluated bacteria have the ability to promote millet growth under conditions of low K availability and have potential for future bioinoculants.