Identification of Potential Minerals/Rocks in Sri Lankan Geological Terrain as Source of Potassium (K) Fertilizer

Due to the agricultural intensification in Sri Lanka, there is a high demand for potassium (K)-fertilizer inputs. However, in the Sri Lankan geological setting, the presence of major potash sources is minimum though the K- bearing minerals and rocks are abundant. Therefore, exploration of K-bearing mineral deposits is essential to cater the demand of K-fertilizer in the country. In this regard, this research is focused on investigating the K-bearing minerals and rocks in Sri Lankan geological terrain which can be used as K-fertilizers directly or as alternatives for currently available K-fertilizers. During sample collection, K-bearing minerals, such as feldspar and mica and K-bearing gneiss rock samples were collected from Matale, Kaikawala and Kadugannawa areas. Processed samples were subjected to analyse major oxide concentrations and K concentrations and surface topography. Analyses revealed that the highest actual potassium concentrations were presented in orthoclase feldspar (10.35 w/w%) and then biotite mica (9.95 w/w%) whereas other rocks showed the lowest. Based on the results, biotite mica (Kaikawala) and biotite gneiss (Matale) displayed the highest potential for K recovery, whilst the least potential for K recovery was shown in orthoclase feldspar (Kaikawala). However, further studies are recommended to develop this K-fertilizer and to assess whether its application is economically viable.