Enhancing organic and inorganic carbon sequestration in calcareous soil by the combination of wheat straw and wood ash and/or lime.

Increasing organic carbon sequestration in agricultural soils is important for improving soil fertility and mitigating climate change. Wood ash is generally applied as a potassium fertilizer, but the effects of simultaneous incorporation of wood ash and crop straw on the turnover of soil organic carbon (SOC) and inorganic carbon (SIC) are not well understood. In this study, a 118-day lab incubation experiment was conducted using a calcareous soil (with 10 years of continuous maize cropping history) to study the effects of adding wheat straw, wood ash and lime. Our study showed that straw addition led to an increase in both SOC (19%) and SIC (3%). Wood ash and lime addition decreased CO2 emission by 182 and 1210 mg kg-1 and increased SIC by 125 and 1001 mg kg-1 during the incubation, respectively, which was due to supply of CaO from wood ash and lime. The increase of SOC content was 2.4% due to the addition of lime. In addition to straw addition enhanced straw-derived OC content, the addition of lime also increased straw-derived OC content by 34.5%. This study demonstrated that lime was more effective in reducing CO2 emission and and enhancing SOC than wood ash. In conclusion, adding lime to calcareous soil might be an effective method of enhancing carbon sequestration and slowing climate change.