Soil pH Levels


Plants have evolved to a variety of environmental circumstances. Gardeners who want their plants to grow up healthy need to make sure that the soil not only has appropriate nutrients but also has the right pH level. Applying the right elements to the soil can get the pH in the soil to a level that is beneficial to your plant.


The level of pH is the measurement of how acidic or alkaline a particular object is. Acidic materials have a higher hydrogen ion activity than water, while alkaline materials have a lower ion activity than water. Everything has a pH scale. Acids have a pH level that is below 7, while alkali has a pH value that is above 7. The pH scale is measured from 0 to 14.


According to Mississippi State University, for many plants, too high or too low a pH level can make it difficult for plants to absorb nutrients from the soil. Different plants need different nutrients in order to grow healthy, though plants generally need nitrogen, potassium and phosphorus in order to thrive. The soil contains nutrients and the plant carries the nutrients into the plant. According to NASA's Soil Science Education page, another problem caused by an inappropriate pH range is that bacteria that are needed to make nitrogen usable by plants cannot thrive in soil that has a pH level that is too high or too low. Soils that are too acidic will also cause the plant to take up materials that are actually toxic. Really acidic soil also prevents the absorption of pesticides and fungicides.


Different plants prefer different amounts of acidity or alkalinity. Plants like the hibiscus, hydrangeas and tea roses prefer more acidic soils. Chrysanthemums, day lilies, geraniums, hollyhocks, Shasta daisies and verbenas can survive in soils that are somewhat alkaline. However, few plants can survive in soils that are really acidic or really alkaline.


Rain water and fertilizer are the two biggest factors impacting the pH level of the soil. According to Mississippi State University, organic matter, soil texture, microorganisms, limestone and sulfur also impact the acidity or alkalinity of soil. Ammonium sulfate and aluminum sulfate are very acidic, while sodium nitrate, calcium nitrate, limestone, hydrated lime and hardwood ashes can be very basic.


Changing the pH level of soil can be difficult because there are a variety of elements to the soil that determine the acidity or alkalinity, and one approach that might work with one soil might not work with another.

Keywords: soil pH level, acidic materials, alkali, organic matter

About this Author

Charles Pearson has written as a freelancer for two years. He has a B.S. in Literature from Purdue University Calumet and is currently working on his M.A. He has written three ebooks so far: Karate You Can Teach Your Kids, Macadamia Growing Handout and The Raw Food Diet.