The sixth edition of the Polish Soil Classification (SGP6) aims to maintain soil classification in Poland as a modern
scientific system that reflects current scientific knowledge, understanding of soil functions and the practical requirements of
society. SGP6 continues the tradition of previous editions elaborated upon by the Soil Science Society of Poland in consistent
application of quantitatively characterized diagnostic horizons, properties and materials; however, clearly referring to soil genesis.
The present need to involve and name the soils created or naturally developed under increasing human impact has led to modernization
of the soil definition. Thus, in SGP6, soil is defined as the surface part of the lithosphere or the accumulation of mineral and
organic materials permanently connected to the lithosphere (through buildings or permanent constructions), coming from weathering
or accumulation processes, originated naturally or anthropogenically, subject to transformation under the influence of soilforming
factors, and able to supply living organisms with water and nutrients. SGP6 distinguishes three hierarchical categories:
soil order (nine in total), soil type (basic classification unit; 30 in total) and soil subtype (183 units derived from 62 unique
definitions; listed hierarchically, separately in each soil type), supplemented by three non-hierarchical categories: soil variety
(additional pedogenic or lithogenic features), soil genus (lithology/parent material) and soil species (soil texture). Non-hierarchical
units have universal definitions that allow their application in various orders/types, if all defined requirements are met. The
paper explains the principles, classification scheme and rules of SGP6, including the key to soil orders and types, explaining the
relationships between diagnostic horizons, materials and properties distinguished in SGP6 and in the recent edition of WRB
system as well as discussing the correlation of classification units between SGP6, WRB and Soil Taxonomy