Morphological characteristics and classification of soils formed from acidic sedimentary rocks in North Kalimantan

The morphology of acidic mineral soils explains the evolution that occurs in the soil body during the process of soil formation, which is predominantly influenced by the parent material and climate. Determination of epipedon and endopedon of diagnostic horizons through description and interpretation of soil profile properties is the basis of land classification, as the knowledge of soil properties, capabilities, and utilization. This research was a descriptive study, carried out in North Kalimantan using a survey method at two different locations based on the rock types, namely Location 1 (clay sand sedimentation) and Location 2 (sandstone). The description and interpretation of soil morphology were carried out by observing the nature of the soil profile, then determining the diagnostic horizon and soil classification referring to the Field Observation Guidelines in the Field and Key to Soil Taxonomy. The results of the study found that, based on its morphological characteristics, the soil in Location 1 had brighter colors, lower OC, higher Al solubility, and a thicker horizon compared to the soil in Location 2. Meanwhile, the texture, structure, pH, and consistency were the same. In both soil profiles, umbric epipedon and cambic endopedon were found. Therefore, the soil was classified as Inceptisols. At the sub-order level, Location 1 was classified as Udepts, and Location 2 as Aquepts. At the great group level, the soil in Location 1 was classified as Hapludepts, and the soil in Location 2 as Endoaquepts. This type of soil had low natural fertility therefore the efforts are needed to improve its ability and utilization through amelioration and fertilization technology.