Disponibilidade de enxofre em solos brasileiros.III. avaliação do enxofre-sulfato disponível por extratores químicos
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Data
1993-12
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Antônio Henrique Garcia
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A greenhouse experiment was carried out wíth surface sarnples of 12 soils from States
ofSão Paulo, Minas Gerais and Goiás (Brazil), with carbon contents ranging from 0.5 to 3.03%,
sulphur from O.O 104 to 0.0319% and clay frorn 8 to 60%. Thc available S-S04 was cvaluated by four chcmical extractants: Ca(H2PO.i.h,HP-500 ppm P in 2.0 N acetic acid; 0.5 N ammonium acctate in 0.25 !\J acetic acid; CaC12 0.15% and 0.05 M HCI. Com (Zea mays L.) was grown in two successive crops in the presence of three rates of S (O, 20 and 40 ppm S). in absence and prcsence of liming. Among the chemical extractants, calcium phosphatc in 2.0 N acetic acid provided the be1 perfonnance both in operational tenns and with respect to correlation with dry matter yield and S uptake. Dilute 0.05 M HCl proved to hc thoroughly inadequatc dueto the impossibility of giving clear uncolored extracts suitable for the turbidimetric detennination of S-So4= thereof. The criticai leveis were, in ppm of S: a) Ca(I-Ji P04 1.f-Ii0-500 ppm P in 2.0 N acetic acid -11; b) 0.5 N NH40Ac in 0.25 N acetic acid -17; e) CaC11 O. 15% -19. The criticai leveis of available S-SO/ in soils would be ovcrestimated if evaluated by relative uptake of available sulphur. Turbidimetric deterrninations of S-SO_t have small sensibility in Iow concentrations ofsulphates in soil extracts. One suggest the refining ofanalytical techniques for sulphates, including severa! soil/solution ratios.
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KLIEMANN, Huberto José; MALAVOLTA, Eurípedes. Disponibilidade de enxofre em solos brasileiros.III. avaliação do enxofre-sulfato disponível por extratores químicos. Anais da Escola de Agronomia e Veterinária, Goiânia, v. 23, n. 1, p. 165-186, jan./dez. 1993. Disponível em: <https://www.revistas.ufg.br/pat/article/view/2639/2610>.