Question
QUESTION: Savannah GA. Just found out that my yard has iron in the soil that was brought in at time of construction. My grass is black in areas and dead in others. I have centipede and fertilize as recommended. I have been told to put lime down as well as millorganite but Lowe's is telling me not to put lime down on centipede. I'm getting confused. So I have 3 questions: 1) Do I or don't I put lime down? 2) Is the iron causing my grass to turn black and die? 3)What is the best and most economic way to remedy the situation?

ANSWER: Hi, Your pH should be 6.5 for centipede.  If it's below that, then lime is called for, but no one can tell you that you need lime without first testing your pH.  Iron compounds lower the pH, but I think pH is more likely the culprit than the iron.
Milorganite is a good choice. Let me know what your pH is and then let's talk again.  Jim

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QUESTION: UGA AG Dept results show that in 3 different areas the PH is 4.1, 3.6 and 3.7; lime was put down a few weeks before the testing. Please see attached picture.
Again, what is the best and most economic way to remedy the situation?


Answer
Lime is the cheapest and best fix, but you still need more.  Apply another 40 lbs. per 1000 sq. ft. and then test it again 30 days after applying. You'll need at least 2 applications and probably 3.  Wait 30 days between applications and test each time until the pH is between 6 and 7. Once there, test it every 60 days for the next year and re-apply lime if the pH falls below 6.
I suspect at some point you'll have to lime once a year to keep the pH near 6.5, but we have to get there first and see what it takes to maintain it.  Jim