Carbon sequestration in cropland soils which could be achieved through improved management practices (IPMs) represents an important opportunity to offset a portion of greenhouse gas emissions. North China is the main wheat and maize production region where many IMPs have been widely used during the last several decades, but the effect size and duration of IMPs on soil organic carbon (SOC) sequestration in wheat-maize double cropping system in this region is scarcely studied. In this study, a meta-analysis was conducted to compare the effect size and duration of four IMPs on SOC sequestration in wheat-maize double cropping system in north China. A total of 29 long-term experiments, consisting of 119 paired treatments were compiled in this analysis. The results indicated that the four IMPs of organic manure application (OM), organic manure combined with chemical fertilizer application (MF), straw return (SR) and reduced or no tillage (RNT) all had significant effects on SOC sequestration in the study area. On average, the IMPs of OM, MF, SR and RNT enhanced SOC density by 260, 328, 278 and 134 kg ha -1 yr -1, respectively. The effect duration of OM, MF, SR and RNT on SOC sequestration were about 48, 26, 22 and 18 years, respectively. Accumulation enhancements of SOC for OM, MF, SR and RNT over SOC sequestration period were about 34.7%, 36.1%, 22.0% and 12.7%, respectively. OM and MF could be the appropriate practices on SOC sequestration in wheat-maize double cropping system in the research area.
