EFFECT OF WATER IONIC STRENGTH ON CALCIUM AND MAGNESIUM DESORPTION FROM SOME CALCAREOUS SOILS IN NINEVEH PROVINCE

Abstract

A laboratory study was conducted to determine desorption behavior of Ca+2 and Mg+2 from of solid phase and dissolution of their holding minerals by using quiet water flow of different ionic strength and SAR constructed by miscible displacement technique via two Aridisols disturbed soil columns sampled from Fadhlia and Hamdania locations in Nineveh province northern of Iraq for 10 irrigation cycles elongated for 240 minute, and also to determine Ca+2&Mg+2 and desorption coefficient rates at 298˚ Kelvin. Results referred two desorption process pathways. First denoted to contributing of exchangeable phase in desorption process and enrichment of soil solution with a highly desorption rate. Second stage denotes to dissolution of minerals holding Ca+2&Mg+2 which supply soil solution for long period by water ionic strength action in presence of in common ion. Parabolic diffusion and power function models appeared high significant of desorption process. Water of high ionic strength 11.2×10-5 mole.L-1 gave highest desorption capacity 456.4 c.mole.kg-1 in comparison with that of low ionic strength 1.12×10-5 mole.L-1 24.9 c.mole.kg-1. Highest desorption coefficient rate 35.51 mg. kg-1.mint-½ in Fadhlia location for water of high ionic strength while it reduced to 2.225 mg. kg-1.mint-½ for low water ionic strength. Desorption coefficient rate in Fadhlia was higher than that in Hamdania location due to difference of waters ionic strength.