Quantity-intensity relations of potassium in representative coastal soils of eastern India

Quantity-intensity (Q/I) isotherms were used to evaluate the dynamics of K+ in twelve coastal soils of eastern India. The activity ratio of K+ (AReK) and corresponding changes in labile K+ (±∆K) at equilibrium increased with increasing K+ concentrations. The equilibrium activity ratio of K+ (ARe0K) varied between 0.09 × 10−3 and 7.50 × 10−3 (mol L−1)1/2. The labile K+ (KL) ranged from 0.265 to 0.4 cmol kg−1 constituting 43.8 to 204.5% of 1N NH4OAc extractable K+. The readily available (K0) and fixed K+ (KX) varied from 0.082 to 0.290 and 0.041 to 0.278 cmol kg−1 contributing 22.8 to 84.5 and 15.5 to 77.2% towards KL, respectively. The potential buffering capacities for K+ (PBCK) fluctuated from 16.2 to 85.7 cmol kg−1(mol L−1)−1/2. The K+ potential ranged from 2.38 to 10.76 cmol kg−1(mol L−1)−1/2. The free energy of K+ exchange (−∆G) ranged from −5533 to −2906 calories mol−1 indicating deficient to adequate in available K+. The ARe0K, K0, KX and −∆G had significant positive correlations with pH, CEC, available and reserves soil K+, while there were inverse relationships between PBCK and these soil parameters. A significant positive correlation was found between ARe0Kand K0, K+ saturation, −∆G and significant negative correlation with KX and PBCK. Significant positive correlations were observed between KX and KL and PBCK and significant negative correlations with ARe0K, −∆G and K+ saturation. PBCK had significant negative correlations with K0, −∆G and K+ saturation. The study provided useful information for understanding K+ dynamics in coastal soils and make significant contribution to operational K+ management.