Evaluation of Aggregate Stability Using the Slaking Index Method with Soil Physical Approach in Keduang Sub-Watershed, Indonesia

Abstract

The Keduang Sub-Watershed area has faced multiple natural disasters like landslides, erosion, and flooding because of the poorly managed terrain in the area. This study examines the distribution of the slaking index on agricultural land in the Keduang Sub-Watershed, analyzes the impact of soil type on it, and identifies the soil physical elements that have the most significant influence on it. The study took place in the Keduang Sub-Watershed, Indonesia, utilizing agricultural land from woods, plantations, drylands, and paddy fields with Andisols, Alfisols, Inceptisols, and Entisols soil types. This survey research was supported by laboratory analysis of the soil's physical and chemical properties and used GIS for data interpretation. Soil samples were collected from 22 Land Map Units (LMUs) with 3 replications each, resulting in 66 samples. The SLAKES software assesses the primary parameter, the slaking index. The supporting parameters analyzed were aggregate stability, bulk density, texture, structure, pH, organic C, and Cation Exchange Capacity (CEC). The research showed that soil types in the Keduang Sub-Watershed significantly affect the slaking index value. The slaking index ranged from 0.13-11.63, with the highest values for Andisols in a forest, while the lowest values were Inceptisols in a plantation. The allophane mineral in Andisols was causing the high slaking index. The soil factors determining the slaking index were bulk density and exchangeable K. The lower the bulk density, the higher the slaking index. Meanwhile, the lower the exchangeable K, the lower the slaking index. The land management recommendations based on determinant factors are adding organic material and reducing soil cultivation practices.