Quantity-intensity parameters and forms of potassium in relation to clay mineralogy in some vineyard growing calcareous soils in Western Azarbaijan Province

Quantity-intensity (Q/I) curves and their derived parameters provide general information about soil K availability. The present study was conducted to assess the potassium Q/I parameters including readily exchangeable K (∆Ko), equilibrium activity ratio (ARek), specific K sites (Kx), lineare potential buffering capacity (PBCk), energy of exchange of K (Ek) and their relationships with forms of potassium, clay mineralogy and the properties of 18 surface soils samples belonging to four main subgroups: Typic Endoaquepts, Fluventic Haploxerepts, Typic Calcixerepts and Typic Haploxerepts in the vineyard growing areas of Western Azarbaijan province. X-ray diffraction analysis showed that illite and chlorite were the dominate clay minerals. The ARek values ranged from 0.0014 to 0.019 (moles/L)0.5. The readily exchangeable K (∆Ko) varied from 0.020 to 0.85 (cmol/kg soil). The values of soil solution K (So-K), exchangeable K (Ex-K) and non exchangeable K (NEx-K) varied from 0.070 to 0.56, 0.42 to 1.4 and 0.2 to 2.6 (cmol/kg soil), respectively. There was highly significant positive relationship between NEx-K and illite contents (R2=0.82, P≤0.001). Significant positive correlation observed between PBCK and clay content (r=0.90, P≤0.001) and CEC (r=0.80, P≤0.001). The highest PBCK values were associated with the Typic Calcixerepts soils which had the greatest clay contents and CEC. The highest AReK value was observed in the Typic Calcixerepts soils with high values of exchange also solution potassium while the lowest values was observed in Typic Endoaquept soils with higher chlorite content in the clay fraction. The soils showed high capacities to maintain the potential of K against depletion, as they represented high potential buffering capacities (PBCk) [18-103 (cmolc/kg)/(mol/L)0.5]