Effects of Tillage and Residue Management on Soil Organic Carbon and Total Nitrogen in the North China Plain

A suitable tillage-residue management system is needed in the North China Plain (NCP) that sustains soil fertility and agronomic productivity. The objectives of this study were to determine the effects of different tillage-residue managements for a winter wheat (Triticum aestivum L.) and summer maize (Zea mays L.) double-crop system on soil organic carbon (SOC) and total N pools. No-tillage with residue cover (NTR), no-tillage with residue removed and manure applied (NTRRM), and conventional tillage with residue removed (CTRR) were investigated for 6 yr, based on a uniform N application among treatments. Soil samples were collected at six depths and changes in SOC and total N pools were analyzed. Treatments of NTRRM and NTR sequestered more SOC and total N in the 0- to 5-cm depth than CTRR. In the subsoil (5-60 cm), annual SOC sequestration was 0.01 and -0.40 Mg ha(-1) yr(-1) for NTRRM and NTR, respectively, while CTRR exhibited a significantly positive SOC pool trend. In the whole soil profile (0-60 cm), NTRRM, NTR, and CTRR sequestered SOC at the rates of 0.66, 0.27 and 2.24 Mg ha(-1) yr(-1). When manure was applied to substitute for the N lost from residue removal, the NTRRM tended to accumulate more SOC than NTR, and had similar accumulation as NTR in total N pools, grain yield, and aboveground biomass. Crop residue could be substituted by manure in this double-crop, irrigated system. Conventional tillage, with residue removed, was suitable in soil fertility and agronomic productivity relative to NTRRM and NTR in the NCP.