*2.2. Residues*

Corn stover was collected within one day after harvest in late September from subplots of contrasting fertility under continuous corn and a corn−soybean rotation at the historic Morrow Plots in Urbana, Illinois, USA. The stover samples, consisting of leaves, stalks, husks, and cobs, were allowed to dry for one week in a forced-air oven at 50 ◦C, subsequently ground to <2 mm using a Model 4 Wiley mill (Thomas Scientific, Swedesboro, NJ, USA), and then transferred to air-tight Mason jars for storage at room temperature. Before use, a composite mixture was prepared for each rotation by combining the four different residues according to the proportions given by Pordesimo et al. [35] for aboveground corn biomass. The two mixtures were characterized (Table 2) for organic C, total N, C:N ratio, and major organic fractions by proximate analysis to estimate the water-soluble fraction, lignin, and cellulose + hemicellulose [36].

**Table 2.** Characterization of corn residue mixtures used in incubation study. Data reported as a mean of duplicate or triplicate determinations. Values for total N and water-soluble fraction differ significantly at *p* < 0.001. Crude protein calculated as total N × 6.25 [37].

