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Growing, Growing, Gone! An Experiment on Nitrogen Fertilizers

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Plants need nitrogen to grow healthy stems and leaves. Although nitrogen is the most abundant element in the air we breathe, that form of nitrogen cannot be used by plants. Nitrogen contained in fertilizer, on the other hand, is readily taken up by plants. In this experiment, you will compare plants grown without nitrogen fertilizer to plants grown with nitrogen fertilizer.


Areas of Science
Time Required
Long (2-4 weeks)
Material Availability
Readily available
Very Low (under $20)
Adult supervision recommended during preparation of nitrogen fertilizer solution
La Né Powers
Edited by Sabine De Brabandere, PhD, Science Buddies


The goal of this experiment is to compare the growth of plants with and without added nitrogen fertilizer.


Plants require more than just water and sunlight to grow. They also require many nutrients found in the soil. One of the most important nutrients required for plant growth is nitrogen. Nitrogen is used to build plant proteins and nucleic acids, including DNA.

Nitrogen is found naturally in the atmosphere and in the soil. Even though there is an abundance of nitrogen available, the most common form of nitrogen (N2) cannot be used by plants. Nitrogen can be combined chemically with oxygen or hydrogen to form types of nitrogen compounds that plants can use. These nitrogen compounds can be added to the soil in the form of ammonium (NH4+) and nitrate (NO3-) fertilizers. Plants grow well when fertilizer containing nitrogen is added to the soil, but this method can be expensive and has to be repeated each time the nitrogen in the soil is used up.

Eight plastic pots filled with soil sit in a large plastic tray
Figure 1. Adding fertilizers containing nitrogen to the soil can help plants grow well.

In this experiment, you will compare plants grown without nitrogen fertilizer to plants grown with nitrogen fertilizer. You will observe the effects of nitrogen on the health of the plants by measuring the increase in biomass (the total mass, or weight, of each plant) during the experiment.

Terms and Concepts



Materials and Equipment

Note: Adult supervision recommended during preparation of nitrogen fertilizer solution.

Experimental Procedure

Safety note: Adult supervision required during use of nitrogen fertilizer.
  1. Make sure pots have holes in the bottom to allow the roots to "breathe" and excess water to drain out.
  2. Measure equal amounts of soil into each of the pots.
  3. Moisten the soil in each pot with the equal amounts of water.
  4. Label four pots with "nitrogen fertilizer" and four pots with "no nitrogen added."
  5. Plant seeds in each pot according to seed packet instructions.
  6. Place plants near a sunny window or under a grow light.
  7. Check your plants regularly and water when needed.
    1. Soil should be kept moist.
    2. Water the "no nitrogen added" pots with regular water.
    3. Water the "nitrogen fertilizer" pots with water mixed with nitrogen fertilizer. Follow the fertilizer manufacturer's recommendations for preparing this solution.
    4. All plants should receive the same amount of liquid at each watering.
    5. Keep track of your watering schedule in your lab notebook.
  8. At regular intervals, record observations on the growth of the plants (e.g., height, number of leaves on each plant, etc.) in your lab notebook. For information on scientifically measuring plant growth see the Science Buddies How-to page Measuring Plant Growth.
  9. Here is a sample data table for organizing your data:
  No Fertilizer With Fertilizer
  #1 #2 #3 #4 #5 #6 #7 #8
  • Height
  • # of Leaves
  • Observations
  • Height
  • # of Leaves
  • Observations
  • Height
  • # of Leaves
  • Observations

  1. Allow plants to grow to maturity, then make final measurements of the growth of each plant. The following resource page provides some suggested methods for accurately quantifying plant growth: Measuring Plant Growth.
  2. Summarize your results by averaging the "No Fertilizer" and "With Fertilizer" conditions, and prepare one or more bar graphs to compare your measurements. The resource page Data Analysis & Graphs can help you.
  3. Summarize your results or draw conclusions based on your data. Check out the resource page Conclusions if you need help.
  4. Make an attractive Display Board and share your results.
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Ask an Expert

Do you have specific questions about your science project? Our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.


  • Compare different amounts of nitrogen fertilizer to see what the ideal concentration is for growing plants.
  • Experiment with other types of nutrient fertilizers to test their effects on plants.
  • Compare different soil types on germination and young plant growth.
  • The following project might interest you as well: Earthworm Castings — The Ideal Proportion in Soil for Young Garden Plants


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General citation information is provided here. Be sure to check the formatting, including capitalization, for the method you are using and update your citation, as needed.

MLA Style

Science Buddies Staff. "Growing, Growing, Gone! An Experiment on Nitrogen Fertilizers." Science Buddies, 12 Jan. 2020, https://www.sciencebuddies.org/science-fair-projects/project-ideas/PlantBio_p012/plant-biology/nitrogen-fertilizers-plant-growth. Accessed 7 June 2023.

APA Style

Science Buddies Staff. (2020, January 12). Growing, Growing, Gone! An Experiment on Nitrogen Fertilizers. Retrieved from https://www.sciencebuddies.org/science-fair-projects/project-ideas/PlantBio_p012/plant-biology/nitrogen-fertilizers-plant-growth

Last edit date: 2020-01-12
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