Replaceable acidity and content of mobile aluminium in pseudogley soils of the Cacak - Kraljevo basin [Serbia, Serbia&Montenegro]

Presented in the paper are results of determining replaceable acidity and content of mobile aluminium in the humus and subhumus horizons of 102 profiles (54 field profiles, 28 meadow profiles, and 20 forest profiles) of pseudogley soils in the Cacak - Kraljevo basin (Serbia, Serbia&Montenegro). The main attention here was devoted to examination of the content of mobile Al in the A (Ahp + Ah), Eg, and Bltg horizons, for the most part to a depth of 50-70 cm. The test results indicated that replaceable acidity of pseudogley varies from pH 3.6 to 5.2 in the A, Eg, and Blth horizons, but that it is below pH 4.5 in 80% of the tested profiles in the A horizon, 94% of them in the Eg horizon, and 98% in the Bltg horizon. The share of profiles with pH 4.0 increases here from 24% in the A (Ahp + Ah) horizon to 73% in the Eg horizon and 87% in the Bltg horizon. In all three horizons, forest profiles in average show the lowest pH value, while field profiles show the highest. Total replaceable acidity (H+ + Al ions) in all horizons of the tested profiles varies within a wide interval. Replaceable acidity is represented by H+ and Al ions in all of the tested profiles, but their ratio varies greatly in different profiles and horizons of the same profiles. The content of mobile Al also varies within a very wide interval in different profiles and horizons: from 0.2 to 32 mg in the A horizon, from 0.5 to 53 mg in Eg horizon, and from 1 to 58 mg/100g in the Bltg horizon. Field profiles are not so rich with mobile Al as might be expected in view of their high active acidity and low content of adsorbed bases. Meadow profiles are insignificantly richer with mobile Al ions than are field profiles, while forest profiles are mush richer, both in the humus and subhumus horizons. Of 175 tested samples of pseudogley soil with content of mobile Al greater than 10 mg/100 g, 173 exhibited a pH value in KCl 4.0.