Amelioration of Degraded Sodic Soil by Afforestation

Amelioration of sodic soils requires the supply of Ca2+ to replace the excess Na+ present on the soil exchange complex. Tree planting on sodic soil produces CO2 that enhances the solubility of CaCO3 present in the sodic soil, and thus releases an appreciable amount of soluble Ca2+ that replaces Na+ from the exchange complex. The study indicates that the sodic soil gets desodified and becomes suitable for plant growth. The study was carried out in 9-year-old rehabilitated plots in the Sultanpur district of Uttar Pradesh, India, to evaluate the relative effects of Prosopis juliflora, Dalbergia sissoo, and Eucalyptus tereticornis plantations on sodic soil and their tolerance of sodicity. The study showed that the saturated soil paste extract Ca2+ and Mg2+ concentrations increased significantly in all the plantations, whereas Na+ concentration decreased from the surface to lower layers. Due to the reduction in Na+ concentration and increase in Ca2+ and Mg2+ concentration, the Sodium Adsorption Ratio (SAR) also declined in the soil profile. P. juliflora proved more efficient in reducing the pHs, displacing the Na+ from surface to lower layers, and increasing Ca2+, Mg2+ and K+ concentration in comparison to D. sissoo and E. tereticornis plantations. These tree species were effective in bringing about improvement in the saturated soil paste extract properties as reflected by the reduced sodicity and changes in cation and anion concentration of the soil.