Question

Which ion is typically present in soil with high acidity?

Answer 1

The ion typically present in soil with high acidity is aluminum (Al3+). This ion becomes solubilized when soil pH drops below 5.0 and is toxic to plants, with acidification intensified by certain agricultural practices and acidic rainwater.

Step-by-step explanation:

In soil with high acidity, the ion typically present is aluminum in the form of Al3+. When soil pH values drop below 5.0, aluminum becomes solubilized and is highly toxic to plants. This solubilization process can be intensified through intensive agricultural practices, such as anhydrous ammonia for N fertilization, which lead to soil acidification. Moreover, the presence of acidic rainwater can contribute to the increased solubility of aluminum and other ions in the soil.

Answer 2

Acidity in soils comes from H+ and Al3+ ions in the soil solution and sorbed to soil surfaces. While pH is the measure of H+ in solution, Al3+ is important in acid soils because between pH 4 and 6, Al3+ reacts with water (H2O) forming AlOH2+, and Al(OH)2+, releasing extra H+ ions. Every Al3+ ion can create[clarification needed] 3 H+ ions. Many other processes contribute to the formation of acid soils including rainfall, fertilizer use, plant root activity and the weathering of primary and secondary soil minerals. Acid soils can also be caused by pollutants such as acid rain and mine spoilings.