If you want to grow azaleas in a soil that initially has a pH of 6.5 and have been told that you should apply sulfur to reduce the soil pH, you would likely need more sulfur if the soil is a clay Vertisol than if it is an clay Ultisol.

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Quizplus · Accepted Answer

Clay soils are more resistant to pH changes than sandy soils, so in general, more sulfur is needed to lower the pH of a clay soil compared to a sandy soil. The two types of clay soils mentioned in the question, Vertisols and Ultisols, are both classified as clay soils, but Vertisols have a higher clay content and are typically more alkaline, making them harder to acidify than Ultisols. Therefore, more sulfur would be needed to lower the pH of a clay Vertisol compared to a clay Ultisol.

If You Want to Grow Azaleas in a Soil That