Compatibility of granulometric groups determined based on standard BN-78/9180-11 and granulometric groups according to PTG 2008 and USDA texture classes

Abstract

Two groups of soil texture classification, differing in limit diameters for particular soil fractions, are used in Poland. The older groups of classifications consider soil particles as < 1 mm and divide them into sand (1.0-0.1 mm), silt (0.1-0.02 mm) and fine or flowable particles (< 0.02 mm). These classifications are used, in a version which originated in 1956 and here denominated as PTG/Musierowicz 1956 in land quality assessment and elaboration of soil agricultural maps. Newer versions of these classifications - professional standard BN-78/9180-11 (1978) and division of soils in agronomic categories described in 1986 - are used in fertilizer recommendations and in agricultural drought monitoring. According to the new soil texture classification PTG 2008, the upper diameter limit for soil particles is 2 mm and these parts are divided into sand (2.0-0.05 mm), silt (0.05-0.002 mm) and clay (<0.002 mm). This classification is compatible with soil texture classification elaborated by the United States Department of Agriculture (USDA) and most frequently applied worldwide. In this paper, the results of analyses of 1087 soil samples representing almost all granulometric groups existing in older and newer Polish soil texture classifications were considered. On the base of the current and earlier studies, the table with probability of occurrence of granulometric group PTG 2008 or texture class USDA for particular granulometric groups BN-78/9180-11 was prepared. For majority of granulometric groups (pl, ps, psp, pgl, pgmp, gp, gpp, gl, glp, gc, gcp, ip, płi) determined on the base of BN-78/9180-11, it is possible to determine their granulometric group/texture class according to PTG 2008/USDA correctly and, frequently, unambiguously. For granulometric groups pglp, pgm, gs, gsp i and płg it is possible to propose with great probability more than one equivalent according to PTG 2008/USDA, and in other cases more studies are recommended.