Initial acid detergent lignin (ADL) concentration in the corn tissues used to prepare litterbags. Error bars, SE. CC refers to plots continuously planted with corn, while AR refers to plots in which alfalfa was grown previously. Bt, NonBt, and NonBt+I refer to the treatments consisting of planting Bt corn (MON863), its non-Bt isoline, and the non-Bt isoline treated with the insecticide tefluthrin. Different letters indicate statistical differences at P < 0.05 by a post hoc Fisher's least significant difference (LSD) test.