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

Authors: TOUFIQ IQBAL

Abstract: Two aluminum compounds, AlCl_3 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, AlCl_3 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 AlCl_3 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.

Keywords: Aluminum, bioavailability, ES8, ET8, incubation time, soil type

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