Soil organic carbon, nitrogen, and enzyme activity in glaciated-derived agricultural landscapes of the U.S. Midwest

The extent to which terrain and landscape drive soil C and nutrient dynamics remains unexplored for agricultural lands, due to their complex interactions. This study assessed soil organic carbon (SOC), total N, mineralizable SOC (C min ) via an incubation experiment, and beta-glucosidase (BG) activity affected by landscape position in glaciated-derived agricultural soils of northern Indiana. Soil samples from the 0–25 cm depth were collected along 10-point transects following the soil catena . Overall, SOC and N concentrations in the landscape were influenced by soil wetness and organic matter accumulation. Depressions, poorly and very poorly drained soils stored 55–76% more SOC than surrounding upland areas. After 28 days of incubation, depressions, poorly and very poorly drained soils released 1.4 Mg C ha −1 as C min , nearly 2-times more than upland areas (0.8 Mg ha −1 ), likely owing to greater enzyme activity (66.3 and 70.3 μg g −1 soil h −1 in depressions and very poorly drained soils, respectively). Mean C-CO 2 evolution decreased exponentially after 28 days (1.5 to 0.2 μg g −1 h −1 ), being the lowest for depressions and very poorly drained soils. Soils with buried histic epipedons had the highest total SOC stock (188 Mg C ha −1 ) compared to mollic and ochric epipedons (51 and 32 Mg C ha −1 , respectively). These findings inform land managers about SOC retention based on soil type and relief and can guide targeted best management and conservation practices according to landscape zones, which is critical to support long-term soil health and sustainability of crop production systems in glaciated-derived landscapes.