Soil sampling approaches in Mediterranean agro-ecosystems. Influence on soil organic carbon stocks

Studies on the quantities and distribution of soil organic carbon stocks (SOC-S) can help to fill the knowledge gaps in estimating the amount of carbon stored in soils. However, one of the problems of soil organic carbon (SOC) is the high variability in space and time. Over the years, many researchers have studied the soil mainly in two different ways: by pedogenic horizons in entire soil profiles (ESP) or by soil control sections (SCS) with different thicknesses along the profile, and this causes uncertainty in SOC and SOC-S evaluation and assessment. This study analyzed the differences in the SOC-S in northeastern Sardinia (Italy) in Cambisols, following two soil sampling approaches, ESP by pedogenic horizons and SCS (25 cm thick) on these selected land uses: tilled vineyards, no-till grassed vineyards, and former vineyards naturally re-vegetated after abandonment. Average data on total SOC-S (T-SOC-S) estimations were 61.5 Mg ha− 1 and 67.3 Mg ha− 1 for ESP and SCS respectively, indicating significantly higher estimates of T-SOC-S when sampling by SCS. Consequently, the ESP approach is recommended to evaluate and certify SOC-S, while SCS may be preferred for monitoring and soil management interpretation purposes.