Last updated on February 13th, 2026 at 02:10 pm
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 Alkaline
So what if you need to make your soil more alkaline?
To raise soil pH, you can incorporate dolomite (dolomitic lime) into the soil. Dolomite not only increases alkalinity but also adds calcium and magnesium, which are beneficial nutrients for plant growth.
Some ornamental plants — such as barberry, photinia, and lilacs — tolerate slightly alkaline soil. Certain edible crops like kale, peas, asparagus, and cauliflower can also perform well in mildly alkaline conditions.
That said, be careful not to overdo it. A soil pH between 7.0 and 8.0 is considered mildly to moderately alkaline and is suitable for many plants. A pH of 8.5 is quite high and can begin to limit nutrient availability, even for plants that tolerate alkaline soil. That’s why soil testing is so important before making adjustments.
As always, make gradual changes and retest your soil after amendments. Slow adjustments are far better than drastic swings that can stress your plants.
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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