Resumen de Quantity-to-intensity (Q/I) relationships can efficiently characterize intensively cultivated agricultural soils in Bangladesh for better potassium supplying capacity

Nirmal C. Shil, Khairul M. Alam, Mohammad A. Saleque, M.R. Islam, Mohammad Jahiruddin

• Aim of the study: Firstly, to evaluate the K dynamics of soils through a quantity-intensity isotherm study; and secondly, to characterize the soils on the basis of quantity-intensity (Q/I) parameters.Area of study: Gazipur, BangladeshMaterial and methods: Eleven soils collected from major agro-ecological zones in Bangladesh were evaluated for their varying K dynamics parameters, and K supplying capacities of these soils were described.Main results: The Q/I plot showed both linear and polynomial relationships for soils in the study. The eleven soils had labile K ranging from 0.022 in Palashbari clay loam to 1.35 cmol kg-1 in Barisal clay. The latter soil had the highest equilibrium K activity ratio (0.003 mol L-1)1/2 and potential buffering capacity (PBC) (460.4 (cmol kg-1) (mol L-1)1/2). The PBC of soils for non-exchangeable pool (PBCne) was much higher than that of exchangeable pool (PBCe) in most soils. The largest amount of PBCne and PBCe occurred in Barisal clay, Gopalpur clay, Jhalokathi clay and Nachol loam which had a higher K desorption rate than all the other soils. The equilibrium exchangeable K, critical exchangeable K and equilibrium solution K of the soils varied widely (0.0006-0.035, 0.06-0.61 and 0.06-0.604 cmol kg-1, respectively). The added K was converted almost equally for the respective soils, with specific reference to the respective exchangeable and non-exchangeable pool for Barisal clay and Nachol loam.Research highlights: All the studied parameters revealed wide variations among the soils. The linear and polynomial relationships for soils can efficiently characterize intensively cultivated soils in Bangladesh.