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The importance of proper soil pH for the growth of plants and turf areas is certainly not a new subject. In addition to good drainage, proper pH is essential to the health and success of plants in the landscape/nursery or lawn areas. During site assessment, a soil pH test should be one of the first steps to determine if adjustments need to be made in many instances, many thousands of dollars are spent on design, plant selection and purchase, and simple, inexpensive soil pH tests are overlooked. Soil is the foundation for plant health and proper pH is a very important part of this foundation.

There are more complicated tests that can be run on soil to determine nutrient levels, but in many cases a simple pH test is all that is needed. Soil pH is a measurement of the soil’s acidity or alkalinity. It is expressed from 0 (most acid) to 14 (most alkaline). Soil with a pH below 7 is said to be acidic while above 7 would be alkaline or basic (7 is neutral). The pH of a soil indicates the concentration of hydrogen ions held by the soil. Because it is measured on a logarithmic scale, a soil with a pH of 5.0 is 10 times more acid than one with a pH of 6.0 and 100 times more acid than one with a pH of 7.0.

The pH has a significant impact on how plants grow and develop. One of the major ways is by its influence on the availability of nutrients required for plant growth and development. Most of the major nutrients are more available to plants (and turf) when the pH is between 6.0 and 7.0. In very acid or alkaline soils, these nutrients can be “tied-up” and therefore unavailable for plant uptake. Microorganisms in the soil responsible for organic matter breakdown and nitrogen availability are also more active in this range. In addition, metals like aluminum is very acid soils may be at toxic levels for certain plants.

Most vegetables, trees, shrubs and lawn grasses prefer and will grow the best when soil pH is between 6.0 and 7.0. As always there are exceptions. For example ericaceous plants such as rhododendrons, azaleas, mountain laurel and blueberries need a pH of 5.0 to 5.5. Often, poor plant growth is blamed on disease or insects when it is, at least in part, due to improper soil pH levels. Plants that are under stress caused by these levels are also more susceptible to disease and insect attack.

There is no substitute for a soil test to determine pH. Do not guess or assume that most soils tend to be somewhat acidic (although N.Y.S soils are predominately acidic in nature). Amendments (and amount) needed to adjust the pH (either up or down) should be based on a test rather than a wild guess. The situation can be made worse by adding the incorrect amendments or in the wrong amounts. A simple pH test is very worth while for your plants.