Differential soil sampling by depth within surface layer 0–30 cm for monitorig of content and storage of soil organic carbon

Differential soil sampling by depth in thin layers is suggested for monitoring of organic carbon (Corg) content and storage in soils of agroecosystems. Its goal is to obtain acceptable values of minimal detectable difference of Corg content and storage comparing two observation periods and statistically based idea of Corg vertical distribution in surface soil layers in one observation period. Vertical distribution of Corg within layer 0–30 cm can serve as an indirect criterion of Corg sequestration ability in soil in the initial base period of monitoring before direct measuring of Corg in the next observation periods at the same dynamic plot. Graphs of distribution of Corg content, soil density and Corg storage along the soil profile in natural soils are submitted. Three principal variants of Corg content distribution along soil profile and different variants of bulk density vertical distribution in soils of agroecosystems are discussed. Tendencies of increasing variability in Corg content due to increasing depth of soil sampling within layer 0–40 cm in soddy-podzolic (Albic Retisols), light-chestnut (Haplic Kastanozems) soils and chernozems were noted. Spatial variability of Corg storage in thin layers and in generalized layers of different thickness is discussed.