One of the most fundamental aspects of maintaining soil health is balancing pH -- in other words, making sure the soil is neither too acidic nor too basic. pH is measured on a scale from 0 to 14, from most acidic to most basic (also called alkaline), with 7 being perfectly neutral. Typically, your lawn and garden plants will thrive best in slightly acidic soil with a pH around 6 to 6.5, with some exceptions (What is the best pH for my soil?) The farther your soil deviates from this range, the more issues you might experience such as deficiencies or toxicities of essential plant nutrients, since soil pH directly affects their availability status.
Once you get your soil test results, you'll know if your soil pH needs to be adjusted and find out if any amendments are recommended to restore balance: typically lime is added to neutralize acidity, and sulfur is added to neutralize alkalinity. But how long do you have to wait for the amendments to kick in? And is it really such an easy fix?
The tricky thing with pH is that it tends to change gradually over time. The effects of sulfur or lime to change soil pH can take 2-3 months or longer to noticeably kick in, depending on temperature, rainfall, and the texture of your soil. Slow-acting lime amendments can persist in the soil and keep on neutralizing acidity for up to 3 or 4 years! Routine soil testing is the only way to confirm that the desired pH change has occurred and to know whether further treatments are needed. Especially in the case of large pH adjustments of over 1 point, your recommendations often show splitting lime or sulfur amendment into multiple applications, even for consecutive years, to avoid shocking your plants and to make sure the amendment reacts with the soil rather than being washed away by rain or irrigation.
What happens if a follow-up soil test after amendment application doesn't show the pH change you were hoping for? First, keep in mind that there is natural variation in soil, even within your yard. Make sure you're taking a composite soil sample from multiple locations across your testing area so that your results are as representative as possible of overall trends. Secondly, know that pH adjustment takes time. Soils with high CEC, high clay content, and/or high organic matter have a strong buffer capacity, meaning it will take more applications over a longer period of time to achieve a pH change.
In the meantime, keeping up with other amendments to meet your plants' nutrient needs can help them flourish, even with a soil pH slightly outside the ideal range. You can also consider selecting plants tolerant of your soil's native pH. Check out the following links to learn more about managing soil pH!
- Managing acidic soil
- Soil acidity and lime (Michigan State University Extension)
- Managing alkaline (basic) soil
- How to lower soil pH (Ohio State University Extension)
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