Leaching behavior of calcium through soil columns treated with lime, gypsum and fly ash

A leaching study was conducted in the laboratory in order to study the effect of different amendments on transportof Ca through 14 cm soil column packed with acid soil. Sandy loam soil from a maize field was collected; air dried and packed in PVC pipe of 15 cm long and 8.6 cm diameter maintaining a bulk density of 1.5 mg m-3. There were four soil columns consist of: C₁⁻ only soil, C₂⁻ lime (CaCO3) @ 5 t ha⁻¹, C₃⁻ gypsum @ 5 q ha⁻¹ and C₄⁻ fly ash @ 80 t ha⁻¹. The soil columns were leached with distilled water maintaining a flow rate of 15±1 ml h⁻¹. The breakthrough curves for different amendment treated soil columns indicated that highest mean resident time (18 h) was observed with the soil column without any amendment, whereas lowest value (12 h) was observed in gypsum and lime treated soil column. The highest velocity of 1.17 cm h⁻¹ was observed in gypsum as well as lime treated soil column and lowest value of 0.78 cm h⁻¹ in control soil column (no amendment). It was calculated that highest amount of calcium (61.71 mg) was leached from gypsum treated soil column where as lowest value of 16.40 mg was observed in control soil column. The highest percentage of Ca was recovered (82.40%) from gypsum treated soil, whereas lowest value of 2.42% in lime treated soil. In other words, a major portion of Ca remained at exchange complex in lime and fly ash treated soil where as about 82% of Ca leached below 14 cm in gypsum treatment. This indicated that application of gypsum to acid soil neutralizes sub soil acidity and lime neutralizes surface soil acidity. A major portion of Ca in lime and fly ash retain in exchange complex and become available to plants during growing season.