Fig. 4. pH at start and after 48 h in three dilutions of extract of alkaline bio fly ash, with and without pea cultivation. Results from aerated solutions are shown in Fig. 4a, and from non-aerated solutions in Fig. 4b. The dilutions with the ash extract concentrations 0.01, 0.05, and 0.20 (m³ m^–3) had following alkalinities: 1.1, 5.4, and 21.6 (mmol HCO₃^– dm^–3), respectively (n = 3, ±SE).