Figure 1a. Average percent soil carbon remaining in the top 15 cm of soil in two Kansas locations following the initiation of cultivation on previously undisturbed prairie soils. Data presented in the figure represent the average across a variety of crop rotations from 1903-1946. Initial soil organic carbon levels were higher in Hays, KS (2.47%) than in Colby, KS (1.83%). Both locations were cultivated using traditional agricultural practices including tilling the soil and growing annual crops that included wheat, oats, barley, corn, kafir and milo. No manure was applied to the fields. Baseline measurements were calculated using adjacent undisturbed prairies at the culmination of the study. The image is published as Figure 1 in Robertson and Grace (2004) in the journal Environment, Development and Sustainability.