Ph Too High 7.4

Asked June 3, 2015, 7:27 AM EDT

After receiving the results from our soil sample test, it was reported that the ph was too high, especially for our rhododendron garden bed. We know aluminum sulfate is too toxic for rhodos, can we use ammonium sulfate to lower the ph? Thanks Lisa and Dick

Wexford County Michigan

1 Response

Rhododendrons need a soil pH of 4.5 to 5.5. Ammonium sulfate (21-0-0) is a nitrogen fertilizer. If you added what it would take to lower the soil pH, the hideously high amount of nitrogen will kill the plants. You cannot use 21-0-0 to lower a pH that much. You need to use garden or soil sulfur. If those selling fertilizer around you mainly cater to farms, it will be very difficult to find soil sulfur. You may be able to find the 21-0-0. But get garden or soil sulfur. I am guessing that you got directions with the test on how much and when.