Last updated on June 21st, 2026 at 08:54 am
So what exactly is pH? Simply put, pH is a scale that measures how acidic or alkaline your soil is. The scale ranges from 0 to 14. A reading of 7 is considered neutral. Numbers below 7 indicate acidic soil, while numbers above 7 indicate alkaline soil.
Many gardeners assume that neutral soil is always best, but that’s not necessarily true. Some plants prefer acidic soil, while others thrive in alkaline conditions. The key is understanding what your soil is like and choosing plants that will perform well in it.
In much of the Southwest United States, soil tends to be alkaline. This is largely due to low rainfall and ongoing drought conditions. With less rain to leach minerals away, alkaline salts build up in the soil over time. In contrast, regions with frequent rainfall often have more acidic soil because rainwater gradually washes minerals deeper into the ground.
That’s why testing your soil is so important. Before planting, take the time to check your soil’s pH so you can make informed decisions during the growing season. A reliable pH test kit or meter from your local nursery is usually all you need to get started.
Most plants like a Neutral Reading
The image above has the needle at 7 or neutral. These are ideal soil conditions no matter where you live. Changing the soil can be done by adding soil fertilizers, compost, manure, or other nutrients, depending on what plants you want to grow.
How to make your soil more acidic
Tomatoes and chile plants prefer slightly acidic soil, while plants like yucca and yarrow are well adapted to alkaline conditions. If you’re growing tomatoes or chile, aim for a soil pH around 6.5. That slightly acidic range helps these plants absorb nutrients more efficiently and produce better yields.
If your soil needs adjusting, there are several ways to do it — but it’s important to make changes carefully.
To raise pH (make soil more alkaline), gardeners commonly add limestone. To lower pH (make soil more acidic), ammonium sulfate can be used. However, too much ammonium sulfate can burn plant roots, so it must be applied cautiously and according to label directions.
A gentler way to increase soil acidity is by incorporating sphagnum peat moss into the soil before planting. You can also purchase acid-forming fertilizers at most local nursery stores.
In many cases, though, drastic adjustments aren’t necessary. Simply improving your soil with well-composted organic matter can help balance nutrient availability and improve overall plant health without major pH swings.
Plants that like Acidic Soil
Don’t overthink it… You can incorporate then test with a store-bought pH soil tester. Ideally, you want a 5.5 or 6. Remember, the lower the number, the MORE acidic. The HIGHER the number the more alkaline. It took me a long time to understand this simple logic!
How to Make Your Soil More Alkaline
What if your soil is too acidic and you need to raise the pH level?
One of the most common ways to make soil more alkaline is by incorporating dolomite (dolomitic lime) into the soil. Dolomite raises soil pH while also supplying calcium and magnesium, two important nutrients that support healthy plant growth.
Many ornamental plants tolerate slightly alkaline soil, including barberry, photinia, and lilacs. Several edible crops also perform well under these conditions, such as kale, peas, asparagus, and cauliflower.
However, it is important not to overdo it. A soil pH between 7.0 and 8.0 is considered mildly to moderately alkaline and is suitable for many landscape plants and vegetables. Once the pH reaches 8.5 or higher, nutrient availability can begin to decline, making it harder for plants to absorb essential elements such as iron, manganese, and zinc.
This is why a soil test is so important before adding any amendments. Testing allows you to make informed decisions and avoid unnecessary adjustments.
As always, make changes gradually and retest your soil after applying amendments. Slow, measured adjustments are much safer than drastic pH swings, which can stress plants and create additional growing problems.
The most important thing to know is that purchasing good store-bought compost and incorporating it with your native soil will lower or raise acidic or alkaline levels in the soil.
If your test is too acidic or alkaline, your plants will have a hard time taking in the proper nutrients for good overall growth.
Plant nutrition is needed for all plants; they need Nitrogen, Phosphorus, and Potassium. Other nutrients and minerals are needed, but these are the most important.
Test your soil information at New Mexico State University.
You can also ask your local Soil Testing Labs at Cooperative Extension Offices to test your soil. The COVID restrictions have been lifted from most CO-OP offices.
Changing pH in Soil – Acid or Alkaline Conditions
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Paul Guzman is a lifelong Southwest gardener and gardening writer with decades of experience helping homeowners grow beautiful landscapes in the desert Southwest. He writes for Guzman’s Garden Centers in Las Cruces, New Mexico, with contributing expertise from Gary Guzman, owner of Guzman’s Garden Centers. If you have any questions or enjoyed this post, feel free to share your thoughts in the comments below.
