GIS-Based Land Suitability Assessment for Cabbage (Brassica oleracea L.) Cultivation in Post-Eruption Soils of Mount Sinabung, Indonesia

Abstract: Cabbage (Brassica oleracea L.) is an important highland vegetable in Karo Regency, where volcanic landscapes provide agricultural potential but also create heterogeneous soil and erosion constraints. Volcanic eruptions can alter soil reaction, nutrient availability, surface stability, and land accessibility, requiring crop-specific land evaluation for sustainable post-eruption agriculture. This study assessed the actual and potential land suitability for cabbage cultivation in eruption-affected agricultural land in Naman Teran District, Karo Regency, North Sumatra, Indonesia. A Geographic Information System (GIS) was used to delineate 13 Land Mapping Units (LMUs) based on soil type, elevation, and slope. Two eruption-affected LMUs in Sigarang-garang and Sukanalu villages were evaluated using field observations, laboratory analyses of 0-30 cm soil, climatedata for 2015–2024, and the FAO matching approach. Cabbage-specific land requirements were applied consistently throughout the assessment. Mean temperature (20.1°C),growing-season rainfall (583.6-593 mm), drainage, soil depth, salinity, and sodicity were generally favorable for cabbage. However, soil acidity was a major limitation, with pH valuesof 4.37 in LMU 1 and 5.31 in LMU 2. LMU 1 was additionally constrained by a steep 25-40% slope, whereas LMU 2 was limited by low base saturation, low organic carbon, and 15-40% surface rock fragments. Under potential suitability conditions, liming can alleviate soil acidity and organic amendments can improve soil quality,although the steeptopography of LMU 1 remainsa structural constraint. LMU 2 could improve to S3 if soil fertility and surface-rock limitations are effectively managed. These findings demonstrate that post-eruption land suitability cannot be inferred from volcanic soil fertility alone and that crop-specific criteria are essential for reliable land-use recommendations. The integrated GIS-FAO framework provides a practical basis for site-specific soil conservation, fertility management, and rehabilitation planning for cabbage production in volcanic highlands.