Soil Organic Carbon Pools and Indices in Surface Soil: Comparing a Cropland, Pasture, and Forest Soil in the Central Appalachian Region, West Virginia, USA

Soil organic C (SOC) pools have various stabilization mechanisms and turnover times, which change with depth and are highly influenced by land use. Total SOC (TOC), particulate organic carbon (POC), mineral-associated organic carbon (MOC), and carbon management index (CMI) were used as indicators to compare cropland with manure application (CM) and continuous pasture (CP) to a hardwood forest (HF) at soil 0-10 and 10-25 cm depths. Land use, depth, and their interactions had significant influences on TOC, POC, MOC, MOC/TOC ratio, and CMI except for land use main effect on TOC. Compared to HF and CP soils, CM showed significantly larger POC (12.4 g kg(-1)) and smaller MOC (8.36 g kg(-1)) at 10-25 cm; CM had significantly smaller TOC (32.3 g kg(-1)) and MOC at 0-10 cm (11.81 g kg(-1)). CM soil at 10-25 cm had higher soil quality and SOC lability as indicated by a significantly larger CMI value (419.2), while CP soil had lower soil quality and SOC lability at 0-10 cm (83.7) and 10-25 cm (73.6) compared to HF soil. This study implied high sensitivity of cropland and pasture surface SOC to degrade under disturbance, which implies that better management strategies are still needed to improve soil quality for these agricultural systems.