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


The materials required for the experiment are as follows:

-    1 packet of Kentucky bluegrass seeds
-    5 plastic pots
-    enough soil for the 5 pots
-    1 bag of soil sulfur
-    1  bag of grounded limestone
-    1 pH measuring kit
-    1 soil chart
-    a 1m ruler
-    a black marker pen


1.    For this experiment, the independent variable is the pH level of the soil (6.0, 6.5, 7.0, 7.5 or 8.0). The dependent variable is the height of the Kentucky bluegrass. Measure the average height of the grass in each of the 5 pots. The constants (control variables) are the conditions in which the pots are kept (they should be in a place that has the same temperature, humidity and light), the type of grass used, the size of the pots, and the type of soil used.

2.    Pour an equal amount of soil into 5 pots. Using a soil chart, add enough soil sulfur or grounded limestone to the samples of soil so that the pH levels of the soil stand at 6.0, 6.5, 7.0, 7.5 and 8.0. Indicate the pH levels on the pots using a marker pen.

3.    In each pot, press your finger into the soil to create a hole that is an inch deep. Place a Kentucky bluegrass seed in each hole and bury the seeds with the soil. You may put a maximum of 10 seeds in each pot. Some, but not all of the seeds will germinate - and this is to be expected.

4.    Water the seeds everyday for the next 14 days. The same amount of water should be used for each pot. Measure the average height of the grass after 14 days and record this in the table below. 

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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: