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Effect of fertilizer on plant growthFeatured science projectScience project video


This science fair project was conducted to ascertain how the amount of fertilizer used will affect the growth of plants. The science fair project involved using levels of fertilizer lower and higher than that which was recommended by the manufacturer.


Watering a plant with too little or too much fertilizer will slow down its growth.

Scientific Terms

Nutrients, fertilizer, osmosis, molecules



Plants need nutrients to grow and fertilizers are a good source of nutrients that may be lacking in the soil. However too much of anything is not a good thing.

Plants absorb water from the soil into their roots through a process called osmosis. This process will require the salt concentration inside the roots to be higher than the salt concentration of the soil. As a result, water molecules will migrate from the soil into the roots in order to equalize the difference in salt concentration levels in the soil and in the roots.

Using too much fertilizer will increase the salt content of the soil. If the salt concentration of the soil becomes higher than the salt content of the roots, water molecules will migrate out of the root into the soil, causing root burn. This will cause the plant to grow more slowly, become dehydrated and eventually die.

Too little fertilizer will cause prevent the plants from growing at an optimal speed due to the lack of nutrients in the soil.

Therefore using the correct amount of fertilizer recommended by the manufacturer is the safest way for the plants to grow healthily.

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Complexity level:
Project cost ($):
Time required:
1 day to prepare, 10 days for the science project experiment
Material availability:
Easily found at a plant nursery
Safety concerns:

Basic safety requirements