Ammonium sulphate used as fertilizer, affected the charge characteristics of the soils from three profiles sampled from the Moubelia. Kornajora and Jemuasol soil series scattered over different agroclimatic regions of West Bengal. The point of zero charge(PZC) for these soils were below the natural pH of the soils and varied from 2.7 to 3.2. The PZCs' were lowered from 2.9 to 2.7 for the Moubelia and Kornajora series and from 2.8 to 2.7 for the Jemuasol series by incremental addition of sulphate (0, 500, 1500, 3000 mg S kg−1). The charge conveyed to the surface of soil colloids by each increment of sulphate differs from that of the previous increment because each successive increment reacts with a surface with a different net charge. The cation exchange capacity of the soils increased by an average of 1.4 cmol (p+) kg−1 following addition of 3000 mg S kg−1 due to replacement of both water and hydroxyl ions with sulphate on the mineral surface.
Charge characteristics, point of zero charge (PZC), cation exchange, sulphate ion
