Empirical Approach of Leaching Curves for Determining the Efficiency of Reclaiming Saline-Sodic Soils in Sahl El-Tina, Sinai, Egypt

Columns experiment was conducted to determine desalinization and desodification leaching curves of a clay saline-sodic soil. Soil samples were collected from Sahl El-Tina plain, Northern Sinai Governorate, Egypt. Soil columns were amended with agricultural normal gypsum "NG", phosphogypsum "PG" and calcium chloride "CaCl2.2H2O". Gypsum Requirements (GR) were calculated according to USDA equation. Calculated amount of gypsum was mixed with whole soil matrix (30-cm). Leaching was done using intermittent ponding method so as to add portions to the already saturated soil columns; and obtained leachates equal to the added portions. Desalinization and desodification curves showed that all treatments reduced soil salinity and sodicity, with a superiority of calcium chloride in reducing soil salinity and sodicity. In addition, the Hoffman’s approach was adopted to estimate the leaching constant (k) of amendments. Desalinization and desodification curves showed that application of calcium chloride appears to have a strong effect on (k) values. The leaching constants (k) of control, NG, PG and CaCl2.2H2O gave averaged values of 0.39, 0.27, 0.25 and 0.19 for desalinization and 0.35, 0.28, 0.27 and 0.16 for desodification, respectively. The lower values of (k) in CaCl2.2H2O treatment depicted lower amounts of water required for leaching and reclamation compared to other treatments. This study suggests that Leaching curves represent a very good method to determine the efficiency of amendments and the optimum depth of leaching water needed for successful reclamation.