Fig. 1. Average soil organic C concentrations, C/N ratio, and bulk density, 0–100 cm at two long-term cropping system experiments conducted in north central (Kanawha) and northeast (Nashua) Iowa, and a native undisturbed prairie site located 50 km from the Nashua cropping system experiment. Data for soil inorganic C (SIC, g kg^–1) are for Kanawha, the only site with measurable concentration of carbonates.