Anais do XXXIV Congresso Brasileiro de Ciência do Solo

SOIL S FRACTIONS IN OXISOLS AFFECTED BY LAND USE AND PHOSPHOGYPSUM APPLICATION

SUSANA CHURKA BUM⁽¹⁾; DAWIT SOLOMON⁽²⁾; JOHANNES LEHMANN⁽²⁾; EDUARDO FAVERO CAIRES⁽³⁾; LUIS REYNALDO FERRACCIU ALLEONI⁽⁴⁾;
1 - UNIVERSIDADE FEDERAL DO CEARÁ; 2 - CORNELL UNIVERSITY; 3 - UEPG; 4 - ESALQ/USP;

Little information is available regarding the speciation and dynamics of organic sulfur (S) functionalities in highly weathered Brazilian soils. We carried out this study in order to assess the effect of phosphogypsum (PG) application on the form and distribution of organic S pools in soils under no-tillage (NT) and under a native forest site. Solid-state X-Ray Near Edge Structure (XANES) spectroscopy technique was used in the humic substances extracted by 0.1 M NaOH/0.4 M NaF. For all sites and all depths evaluated, reduced and intermediate S species (S0 to S5+) were dominant when compared to the strongly oxidized ones (S6+). More oxidized S species (sulfate ester - S6+) were present in the forest area and in the PG area (rate of PG = 12 t ha-1) in comparison with the control treatment (cropped area without PG application). Changes in land-use practice altered both qualitative composition and distribution of S functional groups in this humid subtropical Brazilian soil under NT.

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