Last questions!!

Sulfur:

Many sulfate compounds are quite soluble, so similar to nitrate, sulfate may be leached from the soil in humid regions. However, most soils have some AEC. Recall that AEC is greater at lower pH due to the protonation of hydroxyl (OH) groups. Consider the diagram in your text in the section of Chapter 12 on sulfur retention and exchange, the figure showing the effect of lowering pH on an Al-oxide. As pH decreases AlO^- --> AlOH --> AlOH⁺ giving the soil colloid net +ve change and AEC; thus SO₄ is attracted to the colloid