pH and Soil Amendments

Now that you’ve read my post on “What’s a pH?”, you may want to know what can be done to either lower or increase your soil’s pH.  Of course, the first thing you need to do is have a reputable university or private laboratory test your soil.    Once you have the lab results, you’ll know if pH needs to move up (more basic) or down (more acidic).

In all my years of gardening, I can safely say that the vast majority of garden soils that I’ve encountered were either too acidic (pH 4.6 – 5.5) or already in a suitable range for plant growth (pH 6.2 – pH 7.2).  However, it’s always possible to encounter a soil with a high pH (pH 7.6 – 8.8) as well.

By no means, will the following suffice to fully explain the dynamics relative to soil pH/soil chemistry/soil type and amendments.  There are complete texts devoted to these topics and some knowledge of basic chemistry is needed to weed through the facts. Hence, the following should be seen as a guide to amend your soil, if deemed necessary.

Should your soil test result in an acidic reading (pH 4.5 to 5.5), it is likely that the test results will offer guidance on the quantity of gypsum (CaCO3) to apply.  This is an easy task and product (CaCO3 / lime) can be purchased at a big box store.  As to knowing how much CaCO3 to apply to your garden, this depends on the soil texture, the soil’s pH level and the target pH you’re hoping to establish.

In the event that your soil’s pH is basic (pH 7.5 – 8.5), the means to lower pH is not as straight forward.  However, the use of fertilizers designed to benefit acid loving plants is one way to temporarily offset the effects of high pH.  Additionally, adding large amounts of compost to your garden will also lower your soils pH, but slowly.  A third factor involves incorporating green manure crops in your garden plot.  Although not considered as an “organic” amendment, fertilizing with Ammonium Sulfate helps to lower soil pH while also adding nitrogen to your garden.

Please, don’t be shy to reach out with any questions or comments regarding this post.  Managing your soil so that its pH is in a suitable range (6.2 – 7.2) for optimum plant growth and development is every gardener’s goal!


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