All the treatments were arranged in a randomized complete block design with three replicates (plot size 2.4 m × 16 m). Winter wheat was seeded between 15 and 20 October, and harvested around 5 June. Then summer maize was seeded 7 d later, four rows per plot being seeded. After harvest, all above-ground crop residues were removed from the field. It is historically common that CMC was homogenously spread out on the soil surface only after summer maize harvest; therefore all plots were ridged by rotary tillage before winter wheat seeding. There was no tillage before summer maize seeding in the experimental area.