Characteristics of Andisols Developed from Andesitic and Basaltic Volcanic Ash in Different Agro-Climatic Zones

This study aimed to identify the characteristics of Andisols under tea plantations affected by different Oldeman's agro-climatic zones, of different ages, and containing different types of volcanic ash material. For this study, three tea plantation estates were chosen, the Ciater Site (CTR), Sinumbra Site (SNR), and Sedep Site (SDP), having Oldeman's agro-climatic zones of A, B1, and B2, respectively. Three profiles (CTR-A, CTR-B, and SNR-A) were created from andesitic volcanic ash, and three profiles (SNR-B, SDP-A, and SDP-B) were created from basaltic volcanic ash materials. The CTR-A, SNR-B, and SDP-B profiles were obtained from Holocene parent materials, while the CTR-B, SNR-A, and SDP-A profiles were derived from Pleistocene parent materials. Soil samples were taken from the soil profiles from depths of 0 to 153 cm incrementally, dependent on each soil horizon thickness. The findings of the study reveal that the age of parent materials and the variance in agro-climatic zones result in considerable differences in soil chemical characteristics, such as pH (H2O), base saturation (BS), and organic C, while the qualities of the basaltic and andesitic volcanic ash parent materials were also shown to be unaffected. All Andisol profiles went through cambic weathering processes. Moreover, the key pedogenetic strategies were the production of short-range-order minerals through the leaching of easily dissolved elements and the coprecipitation of SiO2 and Al2O3 gels. Halloysite was formed by the resilication of short-range-order minerals, while gibbsite was formed by desilication. The XRD analysis indicated that amorphous materials predominated with some HIV and kaolinite minerals were also present.