Quantity-intensity ratio of potassium in gypsiferous soils in Iraq

ABSTRACT In gypsiferous soils, potassium (K) undergoes leaching, precipitation and other reactions that reduce its availability. This study aimed to evaluate the physicochemical behavior of K in gypsiferous soils of the Salahaddin province (Iraq), in twelve locations chosen according to the variation in their soil physical and chemical properties. The K adsorption phenomenon was described by using thermodynamic parameters according to the quantity-intensity ratio (Q/I), with the following results: equilibrium activity ratio of 16 to 48 x 10−5 (mol L−1 )1/2, total labile K of 19 to 80 x 10−3 cmolc kg−1, potential buffering capacity of 22 to 42 cmolc kg−1 (mol L−1)−1/2, free energy of exchange of -1.237 to -1.086 kJ mol−1 and Gapon selectivity coefficient of 3.86 to 5.45 (L mol−1)1/2. All the investigated soils are characterized by good potassium reserves, but low in release.