Distribution of potassium forms in soils under repeated rubber cultivation and virgin forest - Ulaganathan A; Ambily K K; Gilkes R J; Jessy M D; Nair N.U (IRC 2012. International Rubber Conference, 28-31 October 2012, Kovalam, India, Rubber Research Institute of India, Kottayam and IRRDB, Malaysia: Abstracts. pp.141-142.)