The study looked at how the pH and aluminum content in acidic soils in south China are affected by different types of soil and crops grown. They found that limestone fertilization can help reduce aluminum toxicity to crops. The pH of the soil decreased after planting tea, leading to an increase in aluminum content. However, planting paddy rice increased the pH of the soil. This shows that the type of soil and crops grown can impact the acidity and aluminum levels in the soil.