During soil acidification, the availability of cations decreases. Cations are positively charged ions, such as calcium, magnesium, potassium, and sodium, which are essential for plant growth and soil health. In acidic soils (with low pH), the hydrogen ions (H+) concentration increases, which can lead to the leaching of these important cations from the soil solution.
As the pH of the soil drops, the increased hydrogen ions compete with cations for binding sites on soil particles and soil organic matter. This competition can lead to a displacement of cations, decreasing their availability for plant uptake. Furthermore, lower pH can result in the mobilization of certain toxic elements, such as aluminum, which can further hinder cation availability.
Therefore, during the process of soil acidification, the net effect is a reduction in the availability of beneficial cations, negatively impacting plant nutrition and growth.