Unlocking the Carbon Sequestration Potential of Agricultural Soils through Deep Tillage —A Dynamic Life Cycle Analysis Perspective

Abstract

Abstract Background This study assessed deep tillage (DT) as a climate change mitigation strategy, focusing on its historical implementation in Lower Saxony, Germany. Four sites (Drüber, Salzgitter, Elze, and Essemühle) where DT was applied in the 1960s were investigated, and the CANDY carbon balance (CCB) model was used to simulate soil organic carbon (SOC) changes after DT implementation. Additionally, a dynamic life cycle assessment (DLCA) was utilised to evaluate the environmental implications and to quantify the carbon (C) sequestration potential of DTs. Results The CCB model accurately captured spatial variations in SOC changes after DT implementation, highlighting Drüber and Salzgitter as the sites with the highest C sequestration. The model's predictions closely matched the measured values, with a relative error between -6.25 and 4.8% and a root mean square error between 0.4 and 0.6, indicating a robust fit of the CCB model at all sites. The sensitivity analysis of the marginal effects revealed that when DT is applied to optimise the SOC increase, crop residues should be retained in the field. Using the DLCA to assess the long-term effects at all sites after DT was applied, the carbon footprint (CF) of the sequestered SOC ranged from 11.14 t CO2e to 48.73 t CO2e ha-1 for almost 50 years if 100 years was considered the time horizon. Compared to traditional LCA, there was an overestimation of the SOC sequestered, oscillating between 12 and 16% at the sites studied. Conclusion Evaluating whether DT can be implemented as an effective strategy for sequestering C involves understanding key factors, including soil processes after DT, and employing precise impact assessments such as DLCA. While soil type and texture (in particular, clay and silt contents) are primary indicators of SOC sequestration, this study revealed that DT, combined with retained crop residues, was positively correlated with SOC increase. Moreover, DT has emerged as an intriguing climate change mitigation strategy for the agricultural sector.