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The materials required for this science fair project:

-    1 packet of tomato seeds

-    1 packet of corn seeds

-    6 onions

-    5 plastic pots

-    enough soil to fill the 5 pots

-    Ruler (1 meter)


1.    For this experiment, the independent variable is the type of plants planted in the pots. The dependent variable is the growth rate of the plants. This is determined by measuring the average height of the 3 plants in each group and calculating the average height. The constants (control variables) are the size of the pot, the environmental factors (such as sunlight and moisture) the amount of soil and the type of plant used.

2.     5 pots are filled with the same amount of soil.  Seeds and onions are planted in each pot as described below. (More than one seed can be used in each pot in case some of the seeds do not germinate. Once they start to geminate, remove the unwanted plants from the pot)

3.    The pots are labeled as pot A, pot B, pot C, pot D and pot E.

a.    Pot A is planted with 3 tomato seeds

b.    Pot B is planted with 3 onions

c.    Pot C is planted with 3 corn seeds

d.    Pot D is planted with 3 tomato seeds and 3 onions

e.    Pot E is planted with 3 tomato seeds and 3 corn seeds

4.    The height of the plants is measured on the 10th day and the average is calculated for each group.

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Complexity level:
Project cost ($):
Time required:
1 hour to prepare, 10 days for observation
Material availability:
Easily found. May be purchased at a plant nursery.
Safety concerns: