Variability of Soil Development in Hilly Region, Bogowonto Catchment, Java, Indonesia

Abstract

Background and Objectives: In Java, a transitional landscape zone is widely formed and causes specific soil profile development due to strongly affected by unstable geomorphic condition. The assessment of variability of soil development at transitional landscape zone is less studied. So, the objective of this study was to characterize variability of soil development in a transitional landscape zone of Bogowonto Catchment. Materials and Methods: Profile Development Index (PDI) were applied to describe the degree of soil development in nine soil profiles from different part of transitional tertiary and quaternary volcanic-structural landscape. The PDI were used to quantify field properties of soils, like texture, moist consistence, wet consistence, structure, rubification, melanization and pH. Parent material properties were also used as references. The quantified data were analyzed through data normalizing per each horizonto result in profile index and weighted mean profile index. Results: The PDI assessment showed that residual soils had the highest index of soil development compared to human-induced soils and landslide-induced soils. Color index (rubification) and textural index are significant to detect residual soils and induced-soils either by geomorphic process or human induces. The same soil types did not always express similar values of PDI because it was depended on geogenic process affected soil parent materials. The study showed that PDI of soils in the transitional landscape zone was not necessarily correlated with parent rock age due to largely disturbed by unstable geomorphic condition. The significant influence of slope inclination was better than slope arrangement in determining the degree of PDI. Conclusion: There was no sequential pattern of PDI in a transitional landscape zone as an impact of unsystematic inclination along slopes and various geogenic and geomorphic processes. The disturbed soils either by human or by geomorphic processes were less developed than residual soils.