Soil mechanics necessary to run water through the sieves to wash the coarse particles and clods through. A variety of sieve sizes are available. The boundary between sand and silt is arbitrary. According to the Unified Soil Classification System, a #4 sieve (4 openings per inch) having 4.75mm opening size separates sand from gravel and a #200 sieve with an 0.075 mm opening separates sand from silt and clay. According to the British standard, 0.063 mm is the boundary between sand and silt, and 2 mm is the boundary between sand and gravel. The classification of fine-grained soils, i.e., soils that are
Polish Soil Classification described diagnostic horizons, diagnostic materials and diagnostic properties. Soil forming processes are not a part of classification but the relationship between the processes and their morphological effects was taken into account during creating differentiating criteria of diagnostic horizons, materials and properties. The classification derives much of international systems: USDA soil taxonomy (1999) and World Reference Base for Soil Resources - WRB (2006). Polish soil science intellectual tradition has always maintained a balance between genetical-geographic approach (typical for the Russian scientific school) and substantional-geological-petrographic approach (characteristic for Western Europe). Multilateral look at the soil manifested, in all editions of classification, that