Analysis of Soil Quality for Hydrological Disaster Mitigation in Sub-Watershed of Krueng Jreue, Aceh Besar Regency-Indonesia

Land conversion of forest to non-forest has led to a reduction in soil fertility, exhibited by a lower soil quality index value (SQI) in the Sub-Watershed of Krueng Jreue. This study aimed to determine soil quality associated with various land uses using the SQI value approach. SQI is calculated based on the criteria proposed by Mausbach & Seybold (1998), which is suitable for field conditions using analysis of Minimum Data Set (MDS). The parameters analyzed include rooting depth, soil texture, bulk density, total porosity, pH of the soil, C-organic, N-total, P-available, K-exchangeable and soil respiration. The result showed that the quality criteria of the soil in the study area consists of three classes, namely: low, medium and high, which have soil quality index values of 0.27, 0.52, and 0.64 respectively. Based on the study's soil quality criteria, the area of research was mapped accordingly by class: (1) high, covering an area of 14016.98 ha (60.38%); (2) medium, covering an area of 8542,90 ha (36.79%); and low, covering an area of 658,18 ha (2.83%). Types of land use categorized as having high quality, were primary forest, secondary forest and residential area with respective values of 0.66; 0.64, and 0.63. Open land, grassland, moor, rice field and shrubs were of medium quality, with respective values of 0.47; 0.48; 0.52; 0.51 and 0.55. The main and additional components affecting the hydrological disaster vulnerability on soil quality parameters are land use change, and soil properties. The findings of this research have implications structural efforts to mitigate hydrological disasters (dams, catchment wells, biopori, tillage conservation, terracing), and non-structural efforts (maps of soil quality, agroforestry, cover crops, materials of soil conditioner, organic matter). These efforts are necessary to improve and maintain soil quality longitudinally