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Soil carbon sequestration, a climate change mitigation option for agriculture, can either increase or decrease as a result of land management change (LMC) and land use change (LUC). To estimate all greenhouse gas (GHG) exchanges associated with various agricultural systems, life cycle assessments (LCAs) are frequently undertaken. To date LCA practitioners have not had a well-defined procedure to account for soil C in their assessments and as a consequence it is often not included. In this study, various methods used to estimate soil C changes due to (i) LMC and (ii) LUC are examined to assess soil C accounting methodologies in the life cycle inventory (LCI) of agricultural LCAs. A compromise between accuracy and completeness in LCA methods is necessary. A ranking of the preference of soil C accounting methods is suggested based on user expertise and data quality. For large scale assessment, the timing of soil CO 2 emissions should be taken into account. If indirect LUC is relevant, a sensitivity analysis of assessment methods should be conducted because the methods highly affect assessment results. A common soil C accounting method that can be easily applied in agricultural LCA needs to be established and an agreement on indirect LUC methods will facilitate the assessment of LMC and LUC within agricultural LCAs. [ABSTRACT FROM AUTHOR]

Soil plays a significant role in controlling the global carbon (C) cycle. Studies on climate change mitigation have focused entirely on soil organic carbon (SOC) to increase C sequestration and decrease carbon dioxide (CO 2) emissions. In contrast, the contribution of soil inorganic carbon (SIC) to CO 2 emissions is usually neglected because SIC is generally considered to be very stable. However, the significant worldwide increase in soil acidification, mainly because of intensive N fertilization and high atmospheric deposition, causes a considerable decrease in SIC stocks, leading to very high unaccounted CO 2 efflux. Additionally, large areas of acidic soils worldwide are regularly subjected to high SIC applications in the form of lime to remediate acidity, which is another direct source of CO 2 emission. Consequently, global efforts to mitigate climate change through SOC sequestration need a revisit as SIC-borne C losses are significant both in terms of C stocks and soil fertility loss, upon which future SOC sequestration will be reduced. Compared to SOC, wherein C stocks can be increased through management, SIC losses are irreversible and cause significant decline in soil health, ecosystem services, and functions. The present review is the first to summarize the current information about acidification-induced intensified SIC losses and their mechanisms. It included: (i) natural and anthropogenic sources and causes of soil acidification, (ii) losses of SIC as HCO 3 − leaching and CO 2 efflux from calcareous soils (7.5 Tg C yr−1) and liming (273 Tg C yr−1) during acidity neutralization, (iii) the relationship between climate change and SIC stocks, (iv) consequences of SIC depletion in soil-plant-water systems, and (v) strategies to remediate and control soil acidification. We concluded that acidification-induced SIC-borne CO 2 losses are a major C loss pathway and could jeopardize global efforts to mitigate climate change through SOC sequestration. • Acidification-induced soil inorganic carbon (SIC) loss causes high CO 2 emissions. • SIC losses deteriorate soil quality and crop productivity. • Fertilization and management-induced changes in SIC should be included in C models. • Balanced N fertilization with organic residue input reduce but not prevent SIC loss. [ABSTRACT FROM AUTHOR]

Vineyards are usually cultivated in soils characterised by low soil organic carbon (SOC) content and have high risks of soil erosion and degradation. Increasing SOC stocks in these cropping systems has the potential to contribute to climate change mitigation through SOC sequestration and to enhance soil quality. We conducted a meta-analysis and compared the SOC stock response ratio, the SOC stock rate of change, and the SOC sequestration rate in vineyards under different SOC sequestration (SCS) practices relative to conventional management. SCS practices included organic amendments (OA), biochar amendments (BC), returning pruning residues to the soil (PR), no-tillage (NT), cover cropping (CC), and several combinations of these practices. The average SOC sequestration rate of SCS management was 7.53 Mg CO 2 -eq. ha−1 yr−1 to a 30-cm soil depth. The highest SOC sequestration rate (11.06 Mg CO 2 -eq. ha−1 yr−1) was achieved under a combination of OA+NT and the lowest (2.82 Mg CO 2 -eq. ha−1 yr−1) was observed under PR treatments. Field experiments performed in particularly hot and dry bioclimatic zones were associated with lower SOC sequestration rates relative to those performed in more temperate areas. The high SOC sequestration rates obtained for many SCS practices, and the large land area dedicated to viticulture worldwide (7.45 Mha), imply that the adoption of SCS practices in vineyards can contribute to the global efforts to offset atmospheric greenhouse gas concentrations via SOC sequestration to mitigate climate change. • Effects of soil carbon sequestration (SCS) practices were assessed in vineyards using a meta-analysis. • All SCS practices led to soil organic carbon (SOC) accumulation in viticultural soils. • The average SOC sequestration rate was 7.53 Mg CO 2 -eq. ha−1 yr−1. • The impact of SCS management on SOC stocks was climate-dependent. [ABSTRACT FROM AUTHOR]