Soil pH

Asked April 28, 2017, 12:10 PM EDT

My garden soil has a pH of 7.9. What can I add to bring the pH down a bit?

Taos County New Mexico

1 Response

If your soil does not have any residual lime in the soil, then the addition of acidic materials such as sulfur, peat moss or other materials with a low pH can be added periodically to lower the pH. Add 2-3 lbs of sulfur per 1000 sf every 4-6 weeks when the ground is not frozen to help start the process of lowering the pH. Also add peat moss at a rate of 3 cy per 1000 sf (this is about a depth of about 1 inch). You can also use ammonium fertilizers such as ammonium sulfate to help lower pH. Fertilizers, however, should be added at recommended rates based on a soil test. The process to lower soil pH can take several years. If your soil is high in residual lime, then you will have to neutralize the lime before you will get a drop in pH. The process to lower the pH is about the same as with soil with no lime, however it can take a substantially longer period of time to see a drop in pH if you can even achieve it at all. If a soil has 5% lime (calcium carbonate), for example, then an acre of land 6 inches deep will have100,000 lbs (50 tons) of lime that has to be neutralized before you will see a drop in pH. To see if you have lime in your soil place some soil in the palm of your hand and add some vinegar to it. If it fizzes, then there is lime present. A laboratory soil test can determine how much lime is actually present.