The quantity-intensity relationship (Q/I) was used to evaluate thermodynamic parameters of zinc in soils under different agricultural management. Ten soil samples were collected from Mosul city to study zinc distribution of calcium carbonate content in these soils. Generally, Q/I relationship of zinc may provide an index for the strength and quantity of effective zinc supply to plants in soils. The Q/I parameters of zinc were studied to quantify zinc release before and after removing carbonates in the studied soils. Results showed that the zinc activity ratio (AReZn) is related to changes with labile zinc (±ΔZn) at equilibrium and increased together with increasing zinc concentrations, intensity (I) ranged between 0.8584 and 0.9972×10-3 mol/L1/2 before removing carbonates and between 0.0909 and 2.7626×10-3 mol/L1/2 after removing carbonates. The ranges of labile Zinc (ZnL) values before and after removing carbonates were between 0.5755-0.7815 and 0.0009-0.0104 cmol/kg, respectively, while the Zinc (PBCZn) before and after removing carbonates fluctuated from 0.5839 to 0.9104 and 0.00112 to 0.00990 cmol/kg(mol/L)−1/2, respectively. That means calcium carbonate increases exchangeable zinc and zinc capacity at equilibrium conditions. The free energy (−ΔF) ranged between -1.001 and -0.979 kJ/mol before removing carbonates and between -1.319 and -0.841 kJ/mol after removing carbonates. Gapon Selectivity Coefficient (kG) ranged between 0.0193835 and 0.027453 and 0.000045 and 0.00450 (mol/L)1/2 before and after removing carbonates, respectively. Therefore, these results may be used as a reference for zinc soil fertilization, whereas thermodynamic parameters values may be used to predict soil ability to supply available zinc.

The objective of this research was to look into the binary exchange in four calcareous soils. The ion adsorption was carried by Batch equilibrium method used to saturate the soil samples with sodium, potassium, calcium and magnesium ions, separately, to get Sodium–Soil, Potassium–Soil, Calcium–Soil and Magnesium–Soil. The mean Kd (L kg–1) scores in various binary systems were arranged as follows: Calcium – Magnesium (18. 7) > Magnesium– Sodium(18.66) >Magnesium – Calcium (17.69) > Calcium – Sodium (15.59) > Magnesium – Potassium (14.31) > Calcium – Potassium (14.26) > Potassium – Sodium (6.5) >Potassium – Magnesium (6.32) > Potassium – Calcium (5.83) > Sodium – Magnesium (4.09) > Sodium – Calcium (4.01) > Sodium – Potassium (3.38).The average values of vanselow selectivity coefficients in different binary exchange systems of cation followed this order: Sodium – Potassium (9.88) > Sodium – Calcium (8.42) > Sodium – Magnesium (8.31) > Potassium – Sodium (5.92) > Potassium – Calcium (5.55) > Potassium – Magnesium (5.34) > Calcium – Potassium (3.17) > Magnesium – Potassium (3.07) > Calcium – Sodium (2.93) > Magnesium – Calcium (2.39) > Calcium – Magnesium (2.17)> Magnesium – Sodium (1.99).

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.

This research was conducted to study potassium buffering potential behavior in some burned soils of Baweza – Mosul and Zawita- Dohuk , in north of Iraq. Potassium forms and the buffering potential phenomenon were studied by using thermodynamic parameters  according to quantity- intensity ratio (Q/I) at   298  oK) The main results could be summarized as follows A great affection for the firing processto cause a high potassium availability and lost by leaching. The ARKe value ranged widely from 0.02 to 0.08 (mol L-1)1/2, the potassium labile pool (LK) rangedfrom 7.951 to 27.919 cmolc kg-1, the potential buffering capacity (PBCK) ranged between 285.47 and 369.48 cmolc kg-1  (mol L-1)-1/2, the free energy of exchange (-G) were range between 3291.8 and 4819.8 kJ mole-1 and the Gapon selectivity coefficient (kG) values fluctuated within the range 8.44 to 12.88 (L mol-1) 1/2.PF values were 0.018 to 0.025 .