Modelling and Kinetics of Sulphur Sorption in a Typic Haplustalf as Influenced by Long-Term Manures and Fertilizers Additions under Rice Monoculture

Adsorption and desorption characteristics of sulphur were studied on the soil samples collected from the long-term fertilizer experiment under rice monoculture continuously since 1975. The results showed that the extent of sulphur (S) adsorption was relatively higher in the control plot soil than in the S-added plots. Similarly, the adsorption of S was lower in the manure-added soils than the unmanured ones. Among the organic manures, addition of urban compost reduced the rate and amount of adsorption of added S. The adsorption data were described better by the Langmuir adsorption than the Freundlich equation. The values of S sorption maxima (b) and bonding energy constant (K) were highest for control plot soils than the Sand manure-added soils. The desorption of native S was higher in the manured treatment than in the unmanured control. The rate of desorption of native S was higher where inorganic S had been added continuously than in the treatment without addition of S. Among the various kinetic models used, first estimate equation emerged as the best fit followed by Elovich equation and two constant rate equation.