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Science Fair Projects on Soil pH & Grass Growth

Soil pH can greatly impact the way certain plants grow in that soil. Soils with a pH of 7 are considered neutral, with higher pH levels indicating alkalinity and lower pH levels indicating acidity. Chemical compounds can be added to the soil to raise or lower the pH. This fluctuation provides an ideal opportunity for science fair projects, as the effects of pH on the growth rate of grass can be clearly demonstrated.

Proper Soil Sampling
- To demonstrate the affects of pH on grass, determine the pH of the soil you will use for the experiment. Test kits for determining pH are available at greenhouses and garden centers. Laboratory tests may be conducted by your county extension office. In either case, soil samples should be taken from a depth of 3 to 4 inches. Samples should be taken from several places in the same area to ensure accuracy, and all plant debris should be removed. After the soil has been tested, carefully document the pH of the soil and use it to fill several flower pots for your experiment.
Soil pH Modification
- Soil pH can be modified by adding two common lawn products. Soil pH can be raised, or made more acidic, by adding lime. It may be lowered, or made more alkaline, by adding lawn sulfur. Both products are available at garden centers. You can use them to modify the pH of your experimental soils. For a good presentation, try to get at least four or five pots of soil with various levels of acidic, neutral and alkaline pH levels, including one unmodified pot. Each dose of lawn sulfur can take several weeks to take effect. Begin the process well ahead of the time the projects needs to be finished. Carefully document the amount of soil additive you use in each pot and the resulting pH.
Planting Grass
- After you have several pots with various pH levels, you can plant some grass. Plant about a dozen grass seeds in each pot, 1-inch deep and well spread out. Water the grass daily for 14 days before the science fair. After 14 days, the grass will have sprouted and the different growth rates should be quite apparent. Lusher grasses such as bluegrass and zoysia are more sensitive to soil pH conditions than hardier types such as fescue. Keep this in mind when choosing which grass seed to plant.
Controlling the Experiment
- To illustrate the affects of soil pH, control as many other variables as possible. Collect the soil from a small area and place it in identical pots. Carefully measure out the water used in each pot to ensure that each is receiving the same amount. Place the pots in a location where they will all receive the same amount of sunlight. Document these control measures and include them in your presentation to demonstrate that the experiment is a valid one.

Nature