Effects of no-tillage systems on soil physical properties and carbon sequestration under long-term wheat–maize double cropping system

• Effects of no-tillage–fertilization system on soil physical properties were estimated.
• The total soil organic carbon did not differ significantly between treatments.
• Three different tillage–fertilization systems were selected in this study.
• NT system increased soil carbon content only in the soil surface layer.

A thorough assessment of changes in soil quality associated with soil management practices is vital for the selection and establishment of sustainable agricultural management. The winter wheat (Triticum aestivum L.)–maize (Zea mays L.) double cropping system was used to study the integrated effects of a 9-year-old tillage coupled with fertilization on soil carbon sequestration and other physical properties in the Yellow River Delta (YRD). Three tillage systems were selected: no-tillage with straw cover plus recommended urea nitrogen rate (NTS), no-tillage with straw removed and manure applied plus recommended urea nitrogen rate (NTM), and conventional tillage with straw removed plus conventional urea nitrogen application rate (CT). There were three replicates of each treatment organized in a randomized block design. NTS and NTM treatments were found to result in a slightly decrease in the soil bulk density (BD), and significantly increased the proportion of water stable aggregates (WSA) (> 2 mm), as well as the water infiltration capacity. The proportion of water stable macroaggregates (> 0.25 mm), the mean weight diameter (MWD) and the geometric mean diameter (GMD) of aggregates in the 0–20 cm layer were unchanged by NTS and NTM. The total soil organic carbon (SOC) stock at a depth of 0–60 cm was not significantly different among the treatments. Both aggregate-associated SOC concentration and stocks (0–5 cm) were significantly greater for NTS and NTM compared with CT, while CT led to a greater OC accumulation in the 20–60 cm soil layer compared with NTS and in the 10–20 cm compared with NTM. The mesoaggregate fraction (2–0.25 mm) and its associated OC pool accounted for the highest percentages in the whole soil profile under the CT treatment. The NT system was found to have a positive effect on the investigated soil physical properties and increase soil carbon content in the soil surface layer. The CT system in conjunction with the wheat–maize double cropping system, however, improved soil aggregation in the soil profile (0–60 cm) and also maintained a higher fraction of SOC in the subsoil compared with the NT systems.