Sulfur doses and pH on the dynamics of S in the soil labile reserve

Abstract

The study of sulfur (S) forms in the soil is relevant, and its availability depends on pH. The aim was to investigate how pH affects the balance between labile and non-labile sulfur reserves. The randomized block design with four replications was used. The treatments were: 1) soil incubated without pH correction; 2) pH corrected to 6.0 before incubation; 3) pH corrected to 6.0 after incubation. An anionic resin membrane was used to determine labile S. The S extracted in 48 hours was readily labile sulfur (RLS), and that extracted after 48 hours was slowly labile and non-labile sulfur (SLS+NLS), obtained from the difference between soil S (after calcination) and RLS. The data was submitted for analysis of variance, and the contrasts were tested (significance at 5%). Hierarchical cluster analysis with complete linkage and Mojena criterion (k=1.25) was also used. The pH correction affected the RLS reserve, increasing its concentration compared to the non-corrected treatment and, consequently, affecting the soil balance between RLS and SLS+NLS. The pH affects the dynamics of the RLS and SLS+NLS reserves, favoring the RLS reserve. There was little influence from the time of correction on these dynamics. Variations influenced the grouping of these soils in texture, mineralogical composition, and organic carbon content. The pH correction before incubation increases sulfate release, especially in soils rich in goethite and gibbsite, affecting the S adsorption according to the soil characteristics.