The porous of this investigation was to study the effect of applied gypsum and or organic compost on improving some physical and chemical properties of sodic and saline sodic soil. A columns experiment was carried out to compare between gypsum and organic compost application either individually or in combinations with each other i.e. 75% of gypsum requirement (GR) + 25% of the standard dose of the organic manure (SDM), 50% of GR + 50% of SDM and 25% of GR + 75% of SDM. The obtained results could be summarized as follows:Application of gypsum, organic compost or combination of both at different ratios decreased soil salinity; the decrease was more pronounced when organic compost was applied alone or combined with gypsum than when gypsum was applied alone. Application of gypsum or organic compost solely or mixed at different ratios markedly decreased the concentrations of Na+, HCO3- and Cl- ions but on the other hand, it increased the concentrations of soluble Ca2+ and SO42- ions. Also, soil pH decreased and the highest decrease was achieved by 50% of GR + 50% of SDM application. Application of 50% of GR + 50% of SDM (NC) was also more effective in decreasing exchangeable Na+ percentage than the other two ratios of mixing gypsum with organic compost. Available contents of N, P and K increased with application of gypsum or compost alone or combined with each other. The highest decreases in soil bulk density and total porosity were obtained when the organic compost was added alone. It was more effective in increasing hydraulic conductivity then the application of gypsum alone or combined with compost. Moreover, application of the organic compost solely resulted in the highest increase in both moisture contents at field capacity and wilting point and consequently the available moisture content. Likewise, gypsum in combination with organic compost at 50% of GR + 50% SDM resulted in the highest value of water stable aggregates.
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