Buffer activity in Cambisol and Podzol induced by acid stress

In the frame of pot experiment with grown plants of spring barley the influ ence of simulated acid load on buffer activity and some characteristics of soil absorption complex and aluminium forms in Cambisol and Podzol was obse rved. Two treatments were applied; treatment 1: watering by distilled water of pH 5.4, treatment 2: watering by acid solution of pH 2.5, respectively. According to theory of Ulrich (1991) PH/H2O values indicate that Cambisol (5.23) is in the so-called silicate and Podzol (4.92) cation exchange buffe r range. Simulated acid load resulted in degradation of silicate buffer sys tem in Cambisol and cation exchange in Podzol what reflected in changes of soil absorption complex. There was found the increase of hydrolytic acidity in Cambisol from 115.3 to 159.1 mmol.kg(-1), in Podzol from 258 to 269.6 m mol.kg(-1), decrease of sum of base exchange cations in Cambisol from 176 t o 160 mmol.kg(-1), in Podzol from 42 to 7 mmol.kg(-1), decrease of base sat uration in Cambisol from 60.4 to 50.5%, in Podzol from 14 to 2.5% (Tabs. I, II). Effect of acid load caused increase of aluminium buffer activity in b oth soil representatives, the increase of labile aluminium Al3+ fraction fr om 149.7 to 397.1 mg.kg(-1) in Cambisol and from 96.2 to 202.5 mg.kg(-1) in Podzol. Consequently, phytotoxic aluminium effect was observed, aluminium concentration in biomass of spring barley increased from 48.5 to 110 mg.kg( -1) in Cambisol and from 58 to 165 g.kg(-1) in Podzol, respectively (Figs. 1, 2). Experimentally ascertained values showed that aluminium solubility i n Cambisol is controlled by composition of mineral part and in Podzol by or ganic matter (Tab. III, Fig. 3).