Influence of induced salinity and sodicity on manganese sorption in vertisols and aridisols

Salinity and sodicity effects on manganese (Mn) sorption in a mixed sodium-calcium (Na-Ca) soil system were studied. Soil samples were taken at 0-30 cm depth from Vertisols (El-Hosh and El-Suleimi) and Aridisols (El-Laota) at three sites in Gezira scheme (Sudan). No Mn was applied to these soils. Prior to analysis the soils were equilibrated with NaCl-CaCL2 mixed salt solutions to attain SAR values at different salt concentrations. The results indicated that saline soils sorbed less Mn and had higher equilibrium Mn concentrations. Sodic soils retained more Mn but had low equilibrium concentrations. Sodicity had a pronounced effect only on increasing Mn retention at higher SAR values. Salinity tended to alleviate sodicity effects on Mn retention, but soluble salts that increased soil pH decreased Mn concentration.