DISTRIBUTION OF PHOSPHORUS IN GRANULOMETRIC FRACTIONS OF CAMBISOL DEVELOPED FROM MORAINIC LOAM

The purpose of the study was to investigate the total phosphorus content in granulometric fractions isolated from the genetic horizons of arable Cambisol developed from morainic loams of the Middle-Polish (Riss) Glaciation, Wartanian Stadial (central Poland). Isolation of granulometric fractions was achieved with application of the Atterberg method without the use of centrifuging and dispersing agents. The total phosphorus content in granulometric fractions increased with a decreasing fraction diameter, and its average content (mg kg(-1)) and contribution in particular fractions (%) was: 1-0.5 mm - 120 (1.1%), 0.5-0.25 mm - 72 (0.6%), 0.25-0.1 mm - 62 (0.5%), 0.1-0.05 mm - 276 (2.5%), 0.05-0.02 mm - 317 (2.8%), 0.02-0.01 mm - 396 (3.5%), 0.01-0.005 mm - 807 (7.2%), 0.005-0.002 mm - 3590 (32.2%), and fraction <0.002 mm - 5489 (49.3%). Fractions of the surface humus horizon (A) and some underlying cambic horizon (Bw) had the highest total phosphorus content, but the lowest contribution to the accumulation of total phosphorus in the soil profile. The enrichment of the surface horizon fractions with phosphorus is the result of its bioaccumulation and fertilisation of this soil, intensively used for agriculture. The leaching process in the soil studied caused migration of phosphorus in the finest fractions (with diameter <0.02 mm) from the humus horizon to the cambic horizon located directly below. However, the small migration depth and particularly the fine graining, coupled with high sorption capacity and low water permeability tested soil, point to limited removal of easily-soluble phosphorus forms from the soil to ground- and surface water.