Reclaiming a saline-sodic,sandy loam soil under rice production

A field-plot reclamation experiment was conducted on a virgin saline-sodic, sandy loam, permeable soil while growing rice with pre- and post-planting leaching under conditions of continuous and intermittent submergence. The soil studied contained very high amounts of soluble salts and exchangeable sodium throughout the profile. The chief salts were Cl^? and SO^2?₄ of Na⁺, Ca²⁺ and Mg²⁺. The data obtained showed that post-transplanting leaching under intermittent submergence alone progressively decreased salinity and sodicity throughout the top 100 cm of the soil to levels safe for cultivation of relatively deep-rooted crops. The surface few centimetres of soil were essentially reclaimed within a few hours after leaching so that young rice seedlings established and survived to give good yield. It was concluded, therefore, that reclamation of these types of soil in arid and semi-arid regions, where good quality water is not available for leaching prior to transplanting rice, would not require any such pre-planting leaching. The results further indicated that there is no need to apply an amendment such as gypsum, mainly because Ca²⁺ and Mg²⁺ present in such soils are adequate to replace the initially high exchangeable sodium during leaching. Leaching efficiency was high under conditions of intermittent submergence. It was shown that leaching curves could be useful in determining the amount of leaching water required for a given mode of application in order to decrease harmful levels of salinity and sodicity to safer levels for a particular crop.