Effect of Active and Total Calcium carbonates ratio on the statue of Potassium in paddy soils

Potassium (K) Quantity- Intensity (Q/I) relationship was utilized to evaluate the potassium status in soils cultivated with rice. Soil samples were collected from three different locations which are Jojer, Segrka and Barvamosa that belong to Akre area in Kurdistan region- Iraq. The results showed that the ratio of active to total calcium carbonates of the locations were (0.179, 0.080 and 0.150) respectively. The available and exchangeable potassium in Segrka were higher than other soils. The Q/I relationship showed that the values of potassium activity ratio at equilibrium (ARek) were (0.83*10-3, 2.99 *10-3 and 1.19 *10-3) (mole L-1)0.5 respectively. The potassium buffering capacity (PBCk) which was (16.77 cmol kg-1(mole L-1)0.5 was the highest inSegrka soil followed by Jojer (15.38 cmol kg-1(mole L-1)0.5) and thenBarvamosa(13.79)cmol kg-1(mole L-1)0.5. The negative values of Gibbs free energy (ΔG) represent spontaneous reaction were (-4202, -3443 and -3988) cal mole-1 respectively, while the value of Gapon selectivity coefficient (KG) were (1.025, 0.838 and 1.085)(L mole-1)0.5respectively. The value of equilibrium exchangeable potassium (EKo) were (1.721, 2.363 and 1.332)cmole kg-1 respectively.