Evaluation of the sulphur status of some soils from Portugal

Abstract

AbstractTotal S, extractable SO4, and SO4− retention capacity were determined in a range of soils covering the dominant soil groups in Portugal which are expected to show S deficiency. Total S was relatively low (83–435 mg S kg−1) in all soils and KH2PO4− extractable SO4 was, in general, low for plant growth, ranging from 0.9 to 32.2 mg S kg−1. SO4− retention capacity ranged from −33.1 to 64.7 mg S kg−1 and was negative in many (14 out of 20) of the soils. Most of the soils are expected to be S deficient and show extensive leaching of SO4. Other selected soil properties that may affect the chemistry of SO4 were determined. A highly significant simple correlation was obtained between SO4 adsorbed and extractable Al by the Mehra and Jackson method (CDB‐Al) (r = 0.74; P < 0.001). A multiple regression which included silt improved the correlation of SO4 adsorbed with CDB‐Al (r = 0.79; P < 0.001).