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The relationship between the pH level of soil and plant growthFeatured science projectScience project video


This science fair project was conducted to examine the relationship between the pH level of soil and plant growth. Specifically, what is the ideal pH level at which Kentucky bluegrass grows? Kentucky bluegrass was grown in soils that had different pH levels (6.0, 6.5, 7.0, 7.5 and 8.0).


The Kentucky bluegrass will grow best in slightly acidic soil.

Scientific Terms

pH, acidic, neutral, alkaline



The pH level of soil can be measured using a pH test kit. Otherwise, one can send a sample of soil to a laboratory to be tested. The test will reveal whether the soil is acidic, neutral or alkaline. Neutral soil has a pH level of 7. Acidic soil has a pH level that is lower than 7. Alkaline soil has a pH level that is higher than 7. Knowing the pH level of soil is important because the pH level determines how well grass will grow.

Grass thrives in slightly acidic soil. If the pH level of the soil is lower than 6.5, it means that the soil is too acidic. Grass cannot grow in it. Grounded lime stone should be added to such soils to raise their pH levels above 6.5. Soil that contains clay and organic materials require a high amount of lime to raise their pH levels. In comparison, sandy soil required a lower amount of lime. After spreading grounded lime stone in the lawn, the lawn should be washed with water in order to remove lime particles from the grass.

Alkaline soil has a pH level that is higher than 7.5. Soil sulfur should be added to alkaline soil in order to lower its pH value. A soil chart can help us to determine how much limestone or soil sulfur we should add to our garden lawns. It takes a month for sulfur to lower the pH level of alkaline soil. Therefore, it is advisable to apply sulfur to alkaline soil in smaller quantities every few weeks, and to regularly  monitor the pH level of the soil.

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Complexity level:
Project cost ($):
Time required:
It will take a day to set up the experiment, and 14 days to conduct it.
Material availability:
The seeds and pots can be purchased from a nursery
Safety concerns: