Bioprospecção de bactérias solubilizadoras de fosfato e inoculação em arroz de terras altas
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Data
2022-05-18
Autores
Oliveira, Jéssica Alves de
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Universidade Estadual Paulista (Unesp)
Resumo
O fósforo (P) é essencial para o desenvolvimento e produtividade das culturas, mas sua concentração nos solos de todo o mundo geralmente está abaixo do ideal. Quando aplicado pela fertilização mineral, é rapidamente fixado aos cátions do solo devido à sua alta reatividade, tornando-se em grande parte indisponível à absorção pelas plantas. Bactérias existentes no solo podem atuar na solubilização do P fixado, liberando-o para a solução do solo, onde fica disponível para absorção pelas plantas. Assim, esta pesquisa teve por objetivo isolar, selecionar e identificar bactérias do solo com potencial para solubilizar fosfatos e avaliar a inoculação dos isolados na redução e/ou eliminação da adubação mineral fosfatada em arroz de terras altas, bem como, seus efeitos sobre o crescimento, a produtividade e a qualidade do arroz. De trinta e dois isolados solubilizadores de fosfatos de cálcio e de ferro, foram selecionados três, por meio de testes in vitro, e posteriormente, identificados como Pantoea sp., Enterobacter sp. e Klebsiella sp. Os isolados foram avaliados em ensaios em casa de vegetação e campo, em esquema fatorial 4 x 3 para as avaliações entre os tratamentos, e 4 x 3 + 2 para as comparações dos tratamentos às testemunhas, com quatro repetições. Os tratamentos foram constituídos pela combinação de quatro doses de P (0; 23,3; 46,6 e 70 kg ha-1), baseadas na utilização de 0, 1/3, 2/3 e 3/3 da dose recomendada para arroz de terras altas com a inoculação dos três isolados de bactérias solubilizadoras de fosfato (BSF) (AAC01 – Pantoea sp.; AAC02 – Enterobacter sp. e AAC04 – Klebsiella sp.). Os tratamentos testemunha consistiram na aplicação de duas doses de P equivalentes a 0 e 70 kg ha-1, sem inoculação. A inoculação de Klebsiella sp. promoveu ganhos significativos tanto no experimento em casa de vegetação, quanto no experimento em campo, com cerca de 33% de redução na adubação fosfatada. No experimento em casa de vegetação, a inoculação de Enterobacter sp. juntamente com a dose de 46,6 kg ha-1 de P aumentou a respiração basal do solo e a massa fresca de parte aérea. A inoculação de Pantoea sp. aumentou a respiração basal do solo de forma linear até a dose de 70 kg ha-1 de P e aumentou a massa fresca da raiz na dose de 46,6 kg ha-1. No entanto, no experimento em campo esses isolados não mantiveram os efeitos. As doses de P utilizadas aumentaram os teores de P dos grãos de arroz, o teor de P nas raízes, a massa seca de parte aérea e a altura das plantas.
Phosphorus (P) is essential for crop development and productivity, but its concentration in soils around the world is generally suboptimal. When applied by mineral fertilization, it is rapidly attached to soil cations due to its high reactivity, making it largely unavailable for plant uptake. Bacteria in the soil can act to solubilize the fixed P, releasing it into the soil solution, where it is available for absorption by plants. Thus, this research aimed to isolate, select and identify soil bacteria with the potential to solubilize phosphates and evaluate the inoculation of the isolates in the reduction and/or elimination of phosphate mineral fertilization in upland rice, as well as its effects on growth, productivity and rice quality. From thirty-two isolates that solubilize calcium and iron phosphates, three were selected through in vitro tests, and later identified as Pantoea sp., Enterobacter sp. and Klebsiella sp. The isolates were evaluated in greenhouse and field trials, in a 4 x 3 factorial scheme for the evaluations between treatments, and 4 x 3 + 2 for the comparisons of treatments to controls, with four replications. The treatments consisted of a combination of four doses of P (0; 23.3; 46.6 and 70 kg ha-1), based on the use of 0, 1/3, 2/3 and 3/3 of the recommended dose for upland rice with the inoculation of the three isolates of phosphate solubilizing bacteria (BSF) (AAC01 – Pantoea sp.; AAC02 – Enterobacter sp. and AAC04 – Klebsiella sp.). The control treatments consisted of the application of two doses of P equivalent to 0 and 70 kg ha-1, without inoculation. The inoculation of Klebsiella sp. promoted significant gains both in the greenhouse experiment and in the field experiment, with about 33% reduction in phosphate fertilization. In the greenhouse experiment, the inoculation of Enterobacter sp. together with the dose of 46.6 kg ha-1 of P increased basal soil respiration and shoot fresh mass. Inoculation of Pantoea sp. increased basal soil respiration linearly up to 70 kg ha-1 of P and increased root fresh mass at 46.6 kg ha-1. However, in the field experiment these isolates did not maintain the effects. The doses of P used increased the P content of rice grains, the P content in the roots, the dry mass of shoots and plant height.
Phosphorus (P) is essential for crop development and productivity, but its concentration in soils around the world is generally suboptimal. When applied by mineral fertilization, it is rapidly attached to soil cations due to its high reactivity, making it largely unavailable for plant uptake. Bacteria in the soil can act to solubilize the fixed P, releasing it into the soil solution, where it is available for absorption by plants. Thus, this research aimed to isolate, select and identify soil bacteria with the potential to solubilize phosphates and evaluate the inoculation of the isolates in the reduction and/or elimination of phosphate mineral fertilization in upland rice, as well as its effects on growth, productivity and rice quality. From thirty-two isolates that solubilize calcium and iron phosphates, three were selected through in vitro tests, and later identified as Pantoea sp., Enterobacter sp. and Klebsiella sp. The isolates were evaluated in greenhouse and field trials, in a 4 x 3 factorial scheme for the evaluations between treatments, and 4 x 3 + 2 for the comparisons of treatments to controls, with four replications. The treatments consisted of a combination of four doses of P (0; 23.3; 46.6 and 70 kg ha-1), based on the use of 0, 1/3, 2/3 and 3/3 of the recommended dose for upland rice with the inoculation of the three isolates of phosphate solubilizing bacteria (BSF) (AAC01 – Pantoea sp.; AAC02 – Enterobacter sp. and AAC04 – Klebsiella sp.). The control treatments consisted of the application of two doses of P equivalent to 0 and 70 kg ha-1, without inoculation. The inoculation of Klebsiella sp. promoted significant gains both in the greenhouse experiment and in the field experiment, with about 33% reduction in phosphate fertilization. In the greenhouse experiment, the inoculation of Enterobacter sp. together with the dose of 46.6 kg ha-1 of P increased basal soil respiration and shoot fresh mass. Inoculation of Pantoea sp. increased basal soil respiration linearly up to 70 kg ha-1 of P and increased root fresh mass at 46.6 kg ha-1. However, in the field experiment these isolates did not maintain the effects. The doses of P used increased the P content of rice grains, the P content in the roots, the dry mass of shoots and plant height.
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Palavras-chave
Oryza sativa L., Cerrado, Fósforo, Solubilização, Inoculante, Phosphorus, Solubilization, Inoculation