Status of Potassium in Intensively Cultivated Soils of Kathmandu Valley

  • K. B. Karki Soil Science Division National Agriculture Research Council, Khumaltar Lalitpur


Five soil profiles were opened at different land uses in Kathmandu valley. They were taxonomically classified as Typic Ustochrept, Dystric Ustochrept, Fluvaentic Ustochrept, Typic Fluvaquents and Aquic Ustochrepts. Their fertility was evaluated using standard guidelines. Different forms of potassium were extracted using 0.5 N HCl, 1N NH4AC, BaCl2 and H2O. Based on the results, the extractants were correlated and also the extracted values. Potassium from both extractants NH4 AC (0.931) and BaC12 (0.934) were best correlated with 0.5 N HC1.The values of K after extraction by different extractants only K from Shanhkamul soils differed from other soils. Potassium from rest of the soil profiles was at par with each other. Considering the status of K in different soils, highest nonexchangeable (0.5NHCl extracted) content 1507.55 mg K/kg was observed in Shnakhamul soil (fluvaentic Ustochrept) and the lowest amount was observed in H2O (3.38mg/kg) extracted Kw in Bungmati soil (Typic Ustochrept ). Only Thimi soils (Typic Fluvaquents) had sufficient exchangeable K and Shankhamul soil had high exchangeable K. Rest of the soils (Typic Ustochrept, Dystric Ustochrept and Aquic Ustochrepts) had insufficient exchangeable K. The amount of nonexchageable K in these soils was not high. Therefore, external application of K in the form of fertiliser is necessary to balance the requirement of this element in these soils.