Release of Ions from Calcium Carbonate Treated Alkali Soil as Influenced by Organic Matter and Moisture Contents

The release of Ca2+ + Mg2+, Na+ and HCO3− ions was studied in an alluvial alkali soil treated with four levels of calcium carbonate viz 0, 10, 20 and 30% (on air-dry weight basis of soil). The treated soil samples were incubated at 32±1°C for 120 days at different moisture regimes i.e. half field capacity, field capacity, saturation and submergence at two levels (0 and 1%) of added organic matter (FYM). Soil sampling was done after 30, 60, 90 and 120 days of incubation and Ca2+ + Mg2+, Na+ and HCO3− concentration were analyzed in saturation extracts. The release of Ca2+ + Mg2+ increased due to dissolution of CaCO3 with increasing level of CaCO3, moisture content, and the effects were more pronounced in the presence of organic matter. Sodium ions increased significantly at submergence and saturation as compared to other moisture regimes. Due to proportionately higher release of Ca2+ + Mg2+ than Na+, there was a net decrease in SAR and more so, at higher moisture regimes and CaCO3 levels. Different kinetic models viz. first order, power function, parabolic diffusion rate and Elovich equations were used to fit the Ca2+ + Mg2+ release data. The value of standard error of estimates (SE) was lowest for first order rate equation and was higher for power function equation, parabolic diffusion rate and Elovich equation. The results suggest that release of Ca2+ + Mg2+ will be more precisely predicted by first order rate equation than others. The higher “a” constant value for organic matter added soils in all the models suggested an instantaneous rate of release of Ca2+ + Mg2+.