Solubilization of iron and aluminum phosphates in
the soil by the fungus F111
Cinthya Babá Barroso1
and Ely Nahas2
1Pós-Graduanda
em Microbiologia- UNESP. E-mail: cbarroso@fcav.unesp.br
2Departamento
de Produção Vegetal. FCAV. Universidade Estadual Paulista-UNESP,
14870-000 Jaboticabal, SP, BRAZIL.
E-mail: e-nahas@fcav.unesp.br
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Some Brazilian soils present a high content of iron and aluminum phosphates and high capacity of fixation of soluble phosphates. This study evaluated the ability of the fungus F111 isolated from soil to solubilize Fe and Al phosphates. Iron, aluminum or calcium phosphate was added to soil samples and inoculated with the isolated F111 (46.2 x 106 spores g-1 soil dry wt). Sugar-cane molasse (2% v/w) was added as a source of carbon on the 1st and 10th day of incubation. Soil samples without molasse, phosphates or fungus were used as control. The soil was incubated at 30ºC for twenty days and samples were removed every 5 days for determination of soil respiration (CO2 production), pH, titratable acidity and soluble phosphate and carbohydrate contents. Soil respiration increased early on the first day after molasse addition and decreased thereafter to the minimum level. The largest contents of soluble phosphorus were observed on the 5th and 15th day of incubation, with the following sequence of phosphate solubilization: aluminum phosphate>iron phosphate>calcium phosphate>control. Another experiment was performed under the same conditions as described above using aluminum phosphate as a source of phosphorus, with evaluations performed daily for 15 days. Aluminum phosphate solubilization was related to CO2 evolution, which increased on the 2nd and 12th day of incubation. Soluble phosphate increased on the 2nd and 11th day and titratable acidity on the 3rd and 11th day. Carbohydrates were decreased after molasse application. Solubilization of insoluble phosphates depended on a carbon source such as molasse but decreased as soon as the carbon source was mineralized in the soil.