Variability of soil mineralogical composition in Sentra Bareh Solok paddy field as affected by eruption material from Mt. Talang

Abstract

Abstract Mt. Talang is one of the active volcanoes in West Sumatra with the last eruption occurred in 2017. The Sentra Bareh Solok paddy field distributed from volcanic middle slope to Singkarak Lacustrine Plain. The composition of sand mineral fraction of nine representative of soil profiles has been analysed using polarization microscope with line counting method. Results show that mineralogical composition are the same, but the amount are different. At the volcanic middle slope, opaque is dominant. It is probably due to thermal formation associated with the melting of existing iron oxides attributed by lava flow. Labradorite and hypersthene are dominant in Alluvial Plain and it could indicate rather slow weathering processes. While, the soils at Lacustrine Plain were dominated by volcanic glass and labradorite and it could be due to silica saturation; more cations and higher pH of soil solution hindering dissolution of minerals. The K-bearing minerals were absent in all soils, indicating K would be the problem as revealed by low K content and its trend decreased from middle slope to the lacustrine. The implication is soils in the Lacustrine Plain and Alluvial Plain would need more K fertilizers than soils in the middle slope.