How Healthy is Your Soil?

With the last weeks of the growing season approaching, now is the time for vegetable gardeners to look at their soil, identify potential improvements that can be made, and begin implementing them. For soils that are lacking in nutrients or those that have a high pH, this is also the best time of year for making more substantial soil amendments, as the upcoming downtime between seasons allows time for amendments to effectively incorporate. As such, September is a perfect time for reviewing soil care basics.

When reviewing the results of a basic soil test, gardeners will often be supplied with measurements of the current pH, phosphorus, and potassium of the sample they have submitted, which, when done correctly, acts as a representative measurement for an entire garden area. The first, pH, is a measure of acidity, and every plant has an ideal range of soil acidity specific to its type. Outside of this range, nutrients may be plentiful in the soil, but physically unable to be absorbed by plants, so amending becomes necessary for proper growth.

For vegetables, ideal soil pH often falls into the just acidic range, with a reading of 6.0-7.0. In the Kansas City region, pH will tend towards the higher, more alkaline end of the spectrum due to the presence of limestone in our soil. As a result, specified rates of sulfur applications may be recommended for incorporation, acting as a gradually effective acidifying agent. This process, however, takes time and may require repeat applications in the spring and fall over several seasons in more severe cases of high pH.

In special instances in this region, pH can also lean towards being too acidic. In such an instance, lime applications may be recommended for raising it. This is also why it is important to avoid lime applications in the area unless you have specifically been instructed to incorporate them, as they can make a bad problem worse. For this same reason, it is not recommended to incorporate wood ash into the soil unless there is a need to raise the pH.

Because pH adjustments take so long to work within the soil, applying them in the fall allows enough time for them to take effect before the spring growing time, but it’s not the only aspect of soil health that can be amended now.

Looking at phosphorus and potassium readings, these nutrients are important because they contribute to cell division (aka growth) and water regulation (turgidity), respectively. Often, if you have fertilized a garden space recently, these nutrients will already be in abundance within a soil profile because they are only used up by plants incrementally. Nevertheless, if a garden has not been fertilized recently and is severely lacking in nutrients, a fall-dormant garden is the only time when non-composted manure amendments are recommended. This is because the amendment will initially be too “hot” in nutrients, capable of burning plants, and it will need some time to cool off and incorporate. Observing the long downtime will also provide enough time for pathogens that could contaminate produce to be killed off, reducing the risk of contamination. No edible portion of a crop should come out of a garden with raw livestock manure amendments until 120 days have passed after application.

Also, bear in mind that overfertilizing with too much manure and/or synthetic fertilizer causes more problems than just those of your plants. An overabundance of nutrients in a soil profile is more likely to leach into waterways during rain, wind, and snow events, eventually accumulating to a point where they cause algal blooms that deplete water of oxygen and result in aquatic die-off. Conducting and following the recommendations of a soil test, your garden will be more likely to thrive, and negative environmental impacts are more likely to be avoided.

The best way to know what your garden soil needs is to test it before adding anything. A basic soil test can help gardeners determine whether nutrients or pH need adjusting and, just as importantly, whether an amendment is unnecessary. Following the recommendations of a soil test can help your garden thrive while reducing the risk of excess nutrients finding their way into local waterways.

If you haven’t tested your garden soil recently, fall is a good time to do it. Johnson County residents can learn more about soil testing, including how to collect a sample and submit it for analysis, through Johnson County K-State Extension’s soil testing resources.

by Anthony Reardon, Horticulture Small Farms Agent, 2026