Forms and Distribution of Potassium in Some Selected Soils of Sahibganj District, Jharkhand, Developed from Rajmahal Trap

Distribution of different forms of potassium (K) was investigated in four representative pedons viz. P1: Lilatanr series (Lithic Ustorthents), P2: Rangamatiya series (Typic Haplustepts), P3: Jetkumarjari series (Vertic Endoaquepts) and P4: Dakshin Balua series (Typic Ustifluvents) developed from Rajmahal trap occurring on various landforms in Borio block of Sahibganj district, Jharkhand. The soils were moderately acidic to moderately alkaline in the surface (pH: 6.0 to 7.9), fine in texture (clay: 25.1 to 53.5%), low in soluble salt content (EC: 0.05 to 0.50 dS m-1), medium to high in organic carbon (OC) (7.3-8.6 g kg-1), and adequate in available K (surface mean 568 kg ha-1). Water soluble K, exchangeable K, non-exchangeable K, lattice K and total K in the soils varied from 0.021 to 0.130, 0.2 to 1.011, 0.10 to 0.839, 36.35 to 86.43 and 38.46 to 88.21 cmol(p+)kg-1, respectively. The profile weighted mean (PWM) of different forms of K revealed the sequence: total K [56.87 cmol(p+)kg-1] > lattice K [55.95 cmol(p+)kg-1] > non-exchangeable K [0.469 cmol(p+)kg-1] > exchangeable K [0.410 cmol(p+)kg-1] > water soluble K [0.046 cmol(p+)kg-1]. The overall contribution of water soluble K, exchangeable K, non-exchangeable K and lattice K to total K were 0.081, 0.721, 0.825 and 98.38%, respectively. Based upon PWM-K, the water soluble K and exchangeable K in the pedons followed the sequence: P4 > P3 > P2 > P1 and P4 > P3 > P1 > P2, whereas nonexchangeable K, lattice K and total K followed the sequence: P4 > P2 > P3 > P1, suggesting maximum quantity of the forms of K in soils of flood plain and minimum in those of foot hills. Vertical distribution of different forms of K revealed no definite trend except water soluble K which showed somewhat gradual decrease down the depth of the pedons. Highly significant positive correlation existed between exchangeable K and available K (r = 0.993**), non-exchangeable K and lattice K (r = 0.864**) and lattice K and total K and (r = 0.999**). A regression equation viz. total K = 32.47 non-exchangeable K = 42.88 (R2 = 0.752) is also proposed.