Soil organic carbon to clay ratio and bulk density related to some basic soil variables in Romania

Abstract This study analyses the soil organic carbon to clay (SOC/clay) ratio, bulk density ( ρ B ) and packing density ( ρ P ) related to some basic soil variables, soil classes and soil types, land uses of various environments, to assess recommendations made by the European Commission (2023). Soil profiles from representative landforms, climate and soils were analysed, and soil properties were processed. In cropland soils, which were found to be the least healthy because of both lower SOC/clay and higher ρ B , SOC/clay values of 1/13 should be a target, not only for the loamy to clayey textures but also for neutral pH to alkaline soils. The ratio of 1/10 should also be a target for grassland soils; for forest soils that generally presented the highest SOC/clay ratios (the healthiest soils), there is no such recommendation. SOC/clay ratio produced some unexpected results within the soil classes and types, characterizing some low‐fertile soils (Psamosols) as healthy, and some well‐structured and rich‐in‐SOC soils (Chernozems, Phaeozems) as unhealthy. Consequently, there is a need to improve this SOC/clay ratio, combining it with other properties, for example, ρ B , texture. ρ B values recommended by the European Commission (2023, Annexes) are too high for Romanian soils, and such recommendations would encourage soil compaction. The proposed ρ B values that start penalizing various crops' yields are 1.77 kg/dm 3 for sandy, 1.73 for loamy‐sandy, 1.67 for sandy‐loamy, 1.63 for loamy, 1.56 for clayey‐loamy texture and 1.44 kg/dm 3 for clayey texture. Using adequate methods to increase SOC, both the SOC/clay ratio and ρ B will be improved.