Fig. 2

Century maize SOC stock change from 1993 to 2012 as estimated by FD and ESM. Average change from 1993 to 2012 in SOC stocks (Mg C ha⁻¹) by soil depth in each maize Century treatment (n = 6 per treatment) as estimated by both FD and ESM, with individual observations represented by black circles. CMT refers to the conventional maize treatment, LMT is conventional maize with winter cover crops, and OMTF is organic maize. We report the results as “ESM depth” intervals [8]. These intervals are the depths represented by the reference soil masses used for the ESM calculation. The reference mass is defined as the mass from the initial fixed depth sample averaged across treatment replicates. Reference masses for each treatment and depth interval can be found in Additional file 1: Table S1a. Error bars represent 95% confidence intervals