Quantity–Intensity Relationships and Potassium Buffering Capacity of Four Ganges River Floodplain Soils M. A. Saleque, 1 M. Anisuzzaman, 2 and A. Z. M. Moslehuddin 3 1 Bangladesh Rice Research Institute Regional Station, Barisal, Bangladesh 2 Kustia Sugar Mills, Jagoti, Kushtia, Bangladesh 3 Soil Science Department, Bangladesh Agricultural University, Mymensingh, Bangladesh Abstract: Ganges river floodplain soil extends from Nepal through India to Bangladesh, which is a good niche for rice–rice and rice–wheat cropping systems in Asia. Application of potassium (K) fertilizer does not give any yield benefits to rice and wheat grown on most of the Ganges floodplain soils in Bangladesh. Understanding of soil K dynamics in this soil is important for the development of K management for rice–rice and rice–wheat cropping pattern in the region. Four Ganges floodplain soils, Sara clay loam, Ghior clay loam, Gopalpur silt, and Ishurdi silt loam, were evaluated for labile K (DK 0 ), K intensity (AR K e ), change in solution (DK), equilibrium exchangeable K (EKo), magnitude of conversion of solution K to exchangeable K (a), and potential buffering capacity of K (PBC K ). The four soils had exchangeable K [ammonium acetate (NH 4 OAc extracted)] of 0.17 to 0.43 cmol kg 21 , with the least in Ishurdi silt loam and the most in Ghior clay loam. The greatest DK 0 (20.81 cmol kg 21 ) was observed in Gopalpur silt, and the least (20.25 cmol kg 21 ) was found in Ishurdi silt loam soil. The four soils exhibited equilibrium AR K e values of 0.007 to 0.021 (mmol L 21 ) 1/2 , with the least in Ishurdi silt loam and the greatest in Gopalpur silt soil. The greatest EK 0 (0.66 cmol kg 21 ) was observed in Ghior clay loam, and the least (0.21 cmol kg 21 ) was in Ishurdi silt loam. Four soils were also Received 10 July 2007, Accepted 27 February 2008 Address correspondence to M. A. Saleque, Bangladesh Rice Research Institute Regional Station, Barisal, P. O. Box 10, Barisal 8200, Bangladesh. E-mail: asaleque_brri@yahoo.com Communications in Soil Science and Plant Analysis, 40: 1333–1349, 2009 Copyright # Taylor & Francis Group, LLC ISSN 0010-3624 print/1532-2416 online DOI: 10.1080/00103620902761320 1333