Potassium Mobility Potential of Forest Soil In Kurdistan Region, Iraq, As Estimated By Quantity- Intensity (Q/I) Relationships

This study aimed to assess potassium(K) 's potential mobility for some soils located in the Kurdistan Region of Iraq. Five soil samples were collected from a depth of (0-30) cm. For each sample, 5g of soil was equilibrated with 50 ml of 0.01 M CaCl2, amended with different K concentrations, and incubated for 24 h at 298 Kelvin. The supernatant was filtered, and K, Ca, and Mg were determined. Potassium exchange equilibrium was calculated from quantity-intensity (Q/I) isotherms. Mean AReK values for all studied soils ranged between 2.4x10-3 to 3.6x10-3(mol L-1)1/2, which reveals that K was preferentially held at inner potions. The amount of labile K(KL) ranged from 0.479 to 1.191cmolc kg-1 in studied soils. The highest value of KL was in Kanypanka while the lowest value was in Goizha. The potential buffering capacity (PBCK) was between 619.56 and 857.37 cmolc kg-1(mol L-1) -1/2. All studied soils were characterized by low percent K saturation and a high ability to replenish K concentration in the soil solution. Gapon selectivity coefficient was relatively high and ranged from 5.64 to 7.88 L mol-1. Higher values of KL indicate a greater K release into the soil solution. Such a high affinity of K to the solid soil phase was attributed to both the elevated organic matter content in these soils and their strong buffering capacities.