Fig. 4. Corn C inputs and corn-derived C remaining in upper 15 cm of soil after 28+ yr of continuous management for no-till (NT) or conventional (moldboard plow) tillage (CT) with residues returned (+) or residues removed (–). Error bars represent standard error. Error bars are not included for "corn input over 28 yr" because values were estimated from yield data. Means with the same letter are not significantly different at a probability of 0.05.