The influence of geological formations on soil characteristics and quality in the southeast region of Pacitan Regency, Indonesia

Abstract

The south eastern region of Pacitan Regency, East Java, Indonesia, is directly facing opposite the direction of the Indo-Australian plate movement, and has a diverse geological structure with different rocks occurring on land surface. This research aims to determine the influence of geological formations on soil characteristics and quality and the limiting factors of soil quality. Soil samples were taken from 40 sampling points from 10 geological formations from the topsoil (tillage layer) at a 0-30 cm depth. The number of sample points is adjusted to the area of the geological formation, where the wider the geological formation, the more samples are taken. Soil characteristics data were analysed using Anova test and Duncan test to get information on the influence of geological formations on soil characteristics. Pearson correlation test and principal component analysis (PCA) were used to calculate the soil quality index, and the Kruskal-Wallis test to analyse the influence of geological formations on soil quality. The result shows that the soil mineral composition is mostly inherited from andesitic-basaltic parent rocks which has experienced weathering. Geological formation has an influence on bulk density, soil water content, porosity, cation exchange capacity and soil organic carbon content. The soil quality index value for various geological formations is in the range of 0.31-0.39, so it is included in the low to medium class. Jaten Formation and the Watupatok Formation do not have limiting factor on soil quality, base saturation (BS) is a limiting factor in Oyo Formation, and soil organic carbon (SOC) and total nitrogen (TN) are limiting factors in almost all geological formations..In conclusion, geological formations signifi cantly influence several soil characteristic parameters but are not the dominant factor determining soil quality.