Elemental sulfur recommendation for pH reduction in soils from Southern Brazil¹

Recomendação de enxofre elementar para a redução do pH de solos do sul do Brasil

HIGHLIGHTS:

Elemental sulfur application is an option to decrease the pH of southern Brazilian soils.

The soil oxidative potential of elemental sulfur can be estimated by its magnesium concentra-tion, acidity, and base saturation.

Decrease the soil pH by one unity required the oxidation of 25 mg of elemental sulfur by kilo-gram of soil.

ABSTRACT

The elemental sulfur (S⁰) application may reduce soil pH, benefiting plants adapted to acid conditions and lessening problems of overliming. Nevertheless, there is no official recommendation for its application. The objective of the study was to quantify the S⁰ doses required to reduce the pH of soils from Southern Brazil. The experiment was carried out in the laboratory in a factorial scheme (5 × 5), with a completely randomized design and three replicates. The treatments consisted of five soils, and five doses of S⁰, corresponding to 0, 50, 100, 150, and 200% of the estimated dose need to reach pH 4.0. The applied doses of S⁰ resulted in reduction of pH and base saturation (V%) and increase of potential acidity (H + Al). These effects, however, were reduced due to the low rate of oxidation of the S⁰ applied (0.76-3.36%). The soil variables correlated with S⁰ oxidation were Mg²⁺ (0.86***), Al³⁺ (-0.82***), H + Al (-0.89***), V% (0.68***) and aluminum saturation (m%) (-0.87***). In the evaluated soils the oxidation of 50 kg ha^-1 of S⁰ was required to reduce one unit of pH in H₂O.

Key words:
sulfur oxidation; sulfate; acidity; overliming