Increasing PH Level

Asked June 15, 2017, 8:08 AM EDT

According to my soil test, my PH level in my backyard is high (7.9) I have a 8 year old River Birch tree in my backyard. I want to lower the PH by applying 2.5lbs of Fast Acting Sulfur (Encap) Link: I read the article in the umn extension page about applying sulfur to reduce the PH level, however, the article did not state when to apply. My question is: When should I apply the fast acting sulfur, and how often? Thank you!!

Dakota County Minnesota

1 Response

It is difficult to lower the soil pH significantly with top dressings after plants are already in the ground. It would have been much better if the soil chemistry problems had been dealt with before the river birch was planted. Inexpensive elemental sulfur is the best product for long term acidification. But it takes months to be effective.

You can introduce elemental sulfur into the soil now by inserting it into holes dug around the tree. It is not as effective as preparing the soil in advance. This article describes the method:

Another way to deal with the high pH soil is to apply a foliar spray of chelated iron. The high pH soil inhibits the roots from taking up iron. With the spray, the tree absorbs the iron directly into the leaves. This is described in the article referred to above.

The product Encap you link to is a mix of 50% elemental sulfur and calcium. The product label tells you frequency (twice a year). It is not a fertilizer - it won't promote growth at the wrong time of year. If you use this product, apply now, then again in the fall, then check soil pH next spring.