Answer: Aluminum sulphate is often used to acidify soil but the amount used would depend on the amount of change needed and on the type of soil you have. When established plants are to be affected it is often better to work somewhat slowly rather than make a drastic pH change. I would strongly suggest you run the basic soil tests and see if that is even the problem -- it may be that poor drainage or wind damage or drought or insect problems are contributing to the yellowing in addition to or even instead of the soil pH. Your County Extension (889-2911) should be able to help you with the soil tests and interpreting the results; they may also be able to determine (based on samples) if that is the cause of the yellowing.
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