The experiment was a split-plot design with four replicates initiated in the fall of 2001 (Liang et al., 2007). The dimension of each main plot was 10.4 m 30 m, each main plot was split lengthwise into two 5.2m 30m sub-plots. Three tillage treat- ments applied at the whole plot level in the experiment were no tillage (NT), ridge tillage (RT) and conventional tillage (CT), and rotations of maize and soybean (Glycine max Merr.) were applied at the sub-plot level with both crops present in each year in each whole plot.