Effect of Al compounds on soil pH and bioavailability of Al in two acid soils

Two aluminum compounds, AlCl3 and Al(OH)3, were used to determine the effect of Al compounds on pH and bioavailability of Al in 2 acid soils. Both soils were incubated for periods of 3, 10, and 30 days. Al-tolerant (ET8) and Al-sensitive (ES8) wheat seedlings were used as a testing plant to confirm bioavailability of Al^3+ in soil solution. Both soils were acidified through the addition of Al compounds to detect the maximum Al^3+ toxicity level of these compounds.The results showed that the AlCl3 compound increased the bioavailability of Al^3+ in soil solutions. In contrast, AlCl3 decreased bulk soil pH. This combination of high levels of extractable Al and low pH decreased the root proliferation of both ES8 and ET8. However, Al(OH)3 did not change soil pH, the bioavailability of Al, or the root length of either ES8 or ET8. These findings indicated that Al(OH)3 did not increase Al^3+ activity in soil solutions. It can be concluded from this study that AlCl3 and a short incubation period can be used to manipulate soil pH and the bioavailability of Al in soil for further study. However, Al(OH)3 cannot be used to manipulate soil pH or the bioavailability of Al in soil.