Genesis of kaolin clay soil across altitudinal gradients in Central Nepal

Abstract Purpose Kaolin group clay soil minerals are crucial for crop protection and soil fertility; However, limited studies have been undertaken in Nepal. So, the comprehensive research was essential to find the kaolin clay soil genesis with regards to altitudinal aspects in central region of Nepal. Methods Five samples of white clay soil were examined from five locations of two sites in Central Nepal, geographically: three from site-1, Daman, Makawanpur, having altitudes 2333, 2332, and 2288 meters above mean sea level and two from site-2, Kaltari, Gorkha having altitudes 543 and 540 meters above mean sea level. The white fine clay was extracted from each sample by a refined procedure and analyzed via X-ray diffraction, scanning electron microscopy, energy dispersive X-ray, and chemical analysis. Results The findings demonstrated that the white clay soils from the two locations contained kaolin group clay minerals, but their proportions and properties differed. Albite (white feldspar) was notably associated with halloysite (7 Å) in the white clay soil samples from Kaltari. The tubular-structured halloysites (7 Å) in the white clay soil from Kaltari presumably resulted from a combination of weathering and hydrothermal alteration of albite. The soils of Daman mostly contained muscovite and albite, with kaolinite, montmorillonite, and halloysite being the main associated minerals. Conclusions This investigation revealed the altitudinal aspect of kaolinite and halloysite (7 Å) (kaolin group) clay formation in the Central Nepal. Kaolin clay soils containing kaolinite and halloysite have been used in protecting crops from insects and diseases. This study will provide a thorough investigation on kaolinite and halloysite clay soils and their possible uses in Nepalese agriculture.