Sulphur to lower pH for iron chlorosis in pin oak trees

I have been using Medicap Fe trunk implants very successfully to fight iron chlorosis in my many pin oak trees for 15 years. Soil samples show my pH to be 7.3 minimum and 7.6 near our long concrete cement driveway. The soil report recommendation is to add 32 pounds of sulphur (sulfur) to a depth of 12 inches per 1000 square feet (or 8 pounds to a 3 inch depth). Several internet sources recommend putting the sulphur in approx. 12 inch deep holes in a 2 foot by 2 foot grid around the tree. They also suggest a 1 to 1 ratio of sulphur and iron sulfate (ferrous sulphate/copperas) to add iron in addition to lowering the pH. Question 1: Will the localized high sulphur concentrations do harm to the trees? Question 2: What is the highest sulphur application rate for grass (lawn) (bluegrass and fescue) without damaging it?
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