The effects of anion types and concentrations on hydraulic properties should be understood in order to model mean soil pore diameter in reactive soils subsequently develop guidelines as an indicator of soil structural stability for sustainable land application of wastewater. Thus, a laboratory experiment was carried out during 2011 in Soils Dept., Faculty of Agric., Mansoura Univ., Egypt, by using an alluvial loamy soil to study the relationship between saturated hydraulic conductivity Ks and mean soil pore diameter (MPD) under three types of sodium salts [0, NaCl, (Na)₂SO₄]and three rates of nitrogen fertilizer as ammonium sulfate (ASF) [0, 100, 150 Kg fed^-1]. The obtained results illustrated that the structural degradation is a function of electrolyte concentration, sodicity and the combined anion of sodium salts. According to that, all the treatments caused a decreasing in MPD subsequently decreasing in the saturated Ks. Correlation coefficients and regression equations were developed to study the dependence of Ks on some physical parameters (MPD and ρb) in studied soil. The mixed NaCl and ASF treatments were the most effective on decreasing MPD and Ks as compared to control, as a result to the specific effect of chloride anion.