Azospirillum brasilense e um isolado solubilizador de fósforo em milho
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Data
2016-06-23
Autores
Moraes, Carime [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
A utilização de micro-organismos que auxiliam no crescimento e nutrição de plantas é uma alternativa promissora para reduzir a dependência de fertilizantes químicos, diminuindo os custos da produção agrícola e também os impactos ambientais causados. Objetivou-se avaliar a solubilização de fluorapatita pelas bactérias A. brasilense e S11 em meio de cultura e avaliar a capacidade desses isolados em promover o crescimento de plantas de milho, além de verificar as alterações químicas e microbiológicas ocorridas no solo decorrente da inoculação das bactérias. O teor de fósforo em meio de cultivo foi verificado diariamente por 7 dias. As plantas de milho foram cultivadas em potes plásticos de 12 dm3 preenchidos com latossolo vermelho escuro em ensaio conduzido em casa de vegetação. Os tratamentos foram dispostos em blocos casualizados, em fatorial (4x2x2), com cinco repetições. Os fatores foram: 1) Inoculação no solo (A. brasiliense, bactéria solubilizadora de fósforo (S11), inoculação com as duas bactérias, controle). 2) Dois níveis de adubação fosfatada: fertilizado e não fertilizado com fosfato de rocha; 3) dois níveis de adubação nitrogenada em cobertura (ausência e presença). Os parâmetros da planta avaliados foram: altura, massa de matéria seca de parte aérea e raiz, enquanto no solo verificou-se a umidade, teor de matéria orgânica, contagem total de bactérias, nitrogênio total, fósforo e carbono da biomassa microbiana. O teor de fósforo solúvel no meio de cultivo variou de 5,26 a 13,56 µg P mL-1para A. brasilense e de 62,04 a 760,55 µg P mL-1para S11. A inoculação com S11 após 336 horas proporcionou o maior valor de fósforo solúvel no meio de cultivo. A aplicação de A. brasilense na ausência de adubação fosfatada aumentou em 10,2% e 28% a altura da planta e matéria seca de folha, respectivamente. Na ausência de adubação fosfatada e nitrogenada a aplicação de bactéria solubilizadora de fósforo aumentou em 44,1% a matéria seca de raiz e 32% a de folha. A umidade do solo não foi afetada pelos fatores avaliados, enquanto que a matéria orgânica foi incrementada pela adubação fosfatada e inoculação de A. brasilense. Após 60 dias da semeadura, a inoculação com S11 isolado ou em combinação com A. brasilense, resultou em aumentos de 4,2 e 3,5%, respectivamente, na densidade de bactérias no solo. A inoculação em conjunto de A. brasilense e S11 na presença de adubação fosfatada e nitrogenada em cobertura proporcionou o maior valor de nitrogênio total no solo. Aumento de 75,9% no fósforo do solo foi obtido com adubação fosfatada e inoculação com A. brasilense. A inoculação de A. brasilense associada a presença de adubação nitrogenada e na ausência de adubação fosfatada promoveu um aumento no carbono da biomassa microbiana.
The use of microorganisms that help the plant growth and nutrition is a promising alternative to minimize the dependence of chemical fertilizers, reducing both costs and the environmental impacts. We aimed evaluate the fluorapatite solubilizing by A. brasilense and S11 bacteria in culture medium, as well evaluate its capacity of promote the maize growth. We also verified the chemical and biological changes in the soil due to the bacteria inoculation. The phosphate content in the cultivation medium was determined daily per 7 days. The maize plants were cultivated in plastic pots of 12dm3 filled out with an Oxisol in an experiment carried out under greenhouse condition. Treatments were arranged in a randomized blocks design in a factorial scheme (4x2x2), with five replications. The factors were: 1) Soil Inoculation (A. brasilense, the phosphorus solubilizing bacteria S11, inoculation with both bacteria, and control). 2) Two levels of phosphate fertilization: with and without rock phosphate. 3) Two levels of nitrogen topdressing fertilization (presence and absence). The evaluated plant parameters were: high, aerial and root parts dry matter mass, soil humidity, organic matter, total bacterial count, total nitrogen and phosphorus, and microbial biomass carbon. The soluble phosphorus content in the mean varied from 5.26 to 13.56 µg P mL-1 to A. brasilense and from 62.04 to 760.55 µg P mL-1 to S11. The S11 inoculation after 336 hours provided the highest soluble phosphorus content in the mean. When we used A. brasilense without the phosphate fertilization the plant was 10% taller and had 28% more dry matter. When we used the phosphorus solubilizing bacteria without neither nitrogen nor phosphorus there was an increase of 44.1% of root dry matter and 32% of leaves. The soil humidity was not affected by the evaluated factors, while the organic matter increased due to the phosphate fertilization and A. brasilense inoculation. After 60 days of seedling, the inoculation with S11 both isolated and combined with A. brasilense presented an increase of 4.2 and 3.5% of bacteria density, respectively. Inoculating both A. brasilense and S11 together to the phosphate and topdressing nitrogen fertilizer, there was a higher content of total nitrogen in the soil. We could observe an increase of 75.9% in the soil phosphorus when combined with phosphate fertilization and A. brasilense inoculation. A. brasilense inoculation together to the nitrogen fertilization and without the phosphate fertilization promoted an increase in the microbial biomass carbon.
The use of microorganisms that help the plant growth and nutrition is a promising alternative to minimize the dependence of chemical fertilizers, reducing both costs and the environmental impacts. We aimed evaluate the fluorapatite solubilizing by A. brasilense and S11 bacteria in culture medium, as well evaluate its capacity of promote the maize growth. We also verified the chemical and biological changes in the soil due to the bacteria inoculation. The phosphate content in the cultivation medium was determined daily per 7 days. The maize plants were cultivated in plastic pots of 12dm3 filled out with an Oxisol in an experiment carried out under greenhouse condition. Treatments were arranged in a randomized blocks design in a factorial scheme (4x2x2), with five replications. The factors were: 1) Soil Inoculation (A. brasilense, the phosphorus solubilizing bacteria S11, inoculation with both bacteria, and control). 2) Two levels of phosphate fertilization: with and without rock phosphate. 3) Two levels of nitrogen topdressing fertilization (presence and absence). The evaluated plant parameters were: high, aerial and root parts dry matter mass, soil humidity, organic matter, total bacterial count, total nitrogen and phosphorus, and microbial biomass carbon. The soluble phosphorus content in the mean varied from 5.26 to 13.56 µg P mL-1 to A. brasilense and from 62.04 to 760.55 µg P mL-1 to S11. The S11 inoculation after 336 hours provided the highest soluble phosphorus content in the mean. When we used A. brasilense without the phosphate fertilization the plant was 10% taller and had 28% more dry matter. When we used the phosphorus solubilizing bacteria without neither nitrogen nor phosphorus there was an increase of 44.1% of root dry matter and 32% of leaves. The soil humidity was not affected by the evaluated factors, while the organic matter increased due to the phosphate fertilization and A. brasilense inoculation. After 60 days of seedling, the inoculation with S11 both isolated and combined with A. brasilense presented an increase of 4.2 and 3.5% of bacteria density, respectively. Inoculating both A. brasilense and S11 together to the phosphate and topdressing nitrogen fertilizer, there was a higher content of total nitrogen in the soil. We could observe an increase of 75.9% in the soil phosphorus when combined with phosphate fertilization and A. brasilense inoculation. A. brasilense inoculation together to the nitrogen fertilization and without the phosphate fertilization promoted an increase in the microbial biomass carbon.
Descrição
Palavras-chave
Adubação nitrogenada, Bactérias promotoras de crescimento de plantas, Fosfato de rocha, Solubilização de fosfato, Zea mays, Nitrogen fertilization, Plant growth-promoting bacteria, Rock phosphate, Phosphate solubilization