ABSTRACT The use of rock dust in Brazil has been studied and encouraged to reduce the Brazilian dependence on the foreign market for chemical fertilizers and as an alternative to organic agriculture. The objective of this research was to evaluate the effects of using phonolite rock powder and organic compound, associated with inoculation with the potassium solubilizing bacteria (KSB) of the genus Burkholderia on the chemical characteristics of the soil, macro and micronutrients in the aerial part, and tomato productivity. The experiment was installed in pots in a greenhouse, using a randomized block design in a 5 × 2 factorial arrangement, representing five doses of phonolite added in an organic compound, with the presence or absence of inoculation with the strain 100-13. The nutrient contents in the soil and the aerial part and the production of tomato were evaluated. Differences were observed between the doses of the organic compound and the phonolite associated with the inoculation. The treatments containing the highest doses of an organic compound provided better levels of nutrients in the soil and the aerial part, and in the tomato productivity. The inoculation with the bacterial strain improved the release of potassium from the powder of the phonolite rock.

RESUMO O Brasil importa a maioria de fertilizantes fosfatados utilizados na agricultura, no entanto, possui em seu território jazidas nacionais que podem suprir parte da demanda do mercado interno. Para que estas possam ser utilizadas de forma efetiva, é necessário identificar técnicas para acelerar a liberação de fósforo (P) destas rochas. Com isso, objetivou-se avaliar a influência da inoculação com estirpes bacterianas solubilizadoras de fosfato (BSF) e decomposição de diferentes resíduos vegetais na solubilização de fosfato natural de Araxá (FNA). Foram realizados dois experimentos em delineamento inteiramente casualizado em esquema fatorial 5 x 4, com quatro repetições. No primeiro foi avaliado a solubilização de FNA por BSF em meio de cultura contendo quatro diferentes fontes de carbono, glicose, sacarose, celulose e pectina. Os tratamentos foram incubados por sete dias e analisou-se a concentração de P e o valor de pH. No segundo, o FNA foi aplicado em 300 cm3 no solo, disposto em câmaras de incubação e adicionados seis gramas de material vegetal seco e triturado de aveia branca, brachiaria, crotalária e tremoço e inoculação das BSF. A decomposição foi avaliada semanalmente pela quantificação do carbono do CO2 (CO2-C) liberado e, aos 42 dias, foi analisado a concentração de P no solo. A fonte de carbono influencia diretamente na solubilização do FNA pelas BSF, destacando-se o gênero Burkholderia. Os tratamentos contendo resíduos de crotalária e tremoço apresentaram maiores valores de CO2-C liberado. Os maiores teores de P no solo foram verificados nos tratamentos contendo resíduos vegetais associado à inoculação BSF.

ABSTRACT Brazil imports most of the phosphate fertilizers used in agriculture, however, it has national deposits in its territory that can supply part of the domestic market demand. In order of these to be used effectively, it is necessary to identify techniques to accelerate the release of phosphorus (P) from these rocks. The objective was to evaluate the influence of inoculation with phosphate solubilizing bacterial isolates (PSB) and decomposition of different plant residues in the solubilization of Araxá natural phosphate (ANP). Two experiments were carried out in a completely randomized design in a 5 x 4 factorial scheme, with four replicates. The first experiment evaluated the solubilization of ANP by PSB in culture medium with four different sources of carbon: glucose, saccharose, cellulose, and pectin. The treatments were incubated for seven days and then were analyzed the P concentration and pH values. In the second experiment, the ANP was applied in 300 cm3 of soil, placed in incubation chambers, with six grams of dry and crushed plant material of white oat, brachiaria, crotalaria, lupine, and the inoculation of PSB. Decomposition was evaluated weekly by quantifying the carbon of the CO2-C released and, after 42 days was analyzed the concentration of P in the soil. It was observed that the carbon source directly influences the solubilization of ANP by PSB, especially the genus Burkholderia. Treatments containing crotalaria and lupine residues showed higher CO2-C values, and the ones containing plant residues associated with BSF inoculation obtained the highest levels of P in the soil.