Spatial Variation of Potassium Quantity/Intensity Relationships and Buffering Capacity of Some Entisols of the Himalayan Floodplain

Abstract

Exchangeable soil potassium (K) determined by NH4OAc may not always be a reliable indicator of K availability to crops. In that case K quantity/intensity (Q/I) relationship could be used to predict its availability in soils. This relationship was used to estimate the K supplying capacity in six surface (0-20 cm) and sub-surface (20-40 cm) soils of Entisols at six different blocks of Cooch Behar district, India situated at Himalayan floodplain. The soils were mostly sandy loam in texture and acidic in pH (5.20 to 6.49). The organic carbon (OC), cation exchange capacity (CEC), clay content and available K were lower in the sub-surface layers (20-40 cm). The plant available K was positively correlated with OC (r = 0.764**, n = 12), clay (r = 0.824**, n = 12) and CEC (r = 0.742**, n = 12). The values of activity ratio of K at equilibrium (ARKe ) in soils varied from 5.3×104 to 15.2×104 in the surface and 3.3×104 to 9.2×104 in the sub-surface layers. The ARKe value was positively correlated with exchangeable K. The total labile pool of K varied with the variation in soil exchangeable K (r = 0.586, n = 12), CEC (r = 0.745**, n = 12) and clay content (r = 0.866**, n = 12). The potential buffering capacity (PBCK) was also much dependent on clay (r = 0.702*, n = 12), OC (r = 0.853**, n = 12) and CEC (r = 0.773**, n = 12) of soil. The lower PBCK values suggest the frequent requirement of K-fertilization for increased crop productivity.