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plants and fertilizer

plants and fertilizer


Without research and the use of fertilizers, today’s human population could not survive. Limited amounts of nutrients in the soil will be consumed by plants in just a few years. We need to feed the soil with nutrients to be able to use it again as a farm land. These nutrients for soil are called fertilizers. These are what plants need to grow.

For many years, humans knew that animal manure can be used as fertilizer. Possibly someone accidentally noticed that plants grow better around animal droppings. They also noticed that burying dead animals next to a tree will help the tree grow faster.
Why animal manure or animal flesh of animals are fertilizers was unknown for many years.

Finally chemical science developed and chemists were able to identify chemical elements and chemical compounds. They tested chemical ingredients of manure and also tested many different chemicals to see which one acts as a fertilizer. These studies and experiments lead to the fact that the main fertilizer elements are Nitrogen, Phosphates and Potassium. The reason that animal manure and dead animals are used as fertilizers is their nitrogen and phosphate contents. Even today meat byproducts and crushed bones are used as nitrogen based and phosphate based fertilizers. Commercial production and use of synthetic fertilizers started around 1850. Synthetic fertilizers are also called inorganic fertilizers.


This project guide contains information that you need in order to start your project. If you have any questions or need more support about this project, click on the “Ask Question” button on the top of this page to send me a message.

If you are new in doing science project, click on “How to Start” in the main page. There you will find helpful links that describe different types of science projects, scientific method, variables, hypothesis, graph, abstract and all other general basics that you need to know.  

Project advisor

Information Gathering:

Find out about what you want to investigate. Read books, magazines or ask professionals who might know in order to learn about the effect or area of study. Keep track of where you got your information from. This is a sample of the information that you may find about fertilizers.

Fertilizers are organic or inorganic material that contain a high level of nitrogen, phosphate, potassium or other nutrients needed for plants growth. Fertilizers must be water soluble in order for the plant to absorb them. Most inorganic fertilizers are 100% water soluble, but organic fertilizers have some water soluble contents.

Organic fertilizers such as animal droppings and animal flesh are not fully water soluble, but they will decompose and create more soluble material as time passes.

Inorganic fertilizer compounds differ greatly in their solubility in water. These differences are usually unimportant for application in the solid form. High solubility, however, is one of the major considerations for the grower who purchases solid fertilizer for dissolving in irrigation water, or for application in foliar sprays. Let’s compare the solubility of a few fertilizers.

Solubility of Some Fertilizers

Compound  Pounds Soluble
in 100 Gallons of Water
 ammonium nitrate  1,617
 urea  902
 ammonium sulfate  623
 di-ammonium phosphate  574
 mono-ammonium phosphate  312
 muriate of potash  283
 potassium nitrate  263
 sulfate of potash  92

Recently attention has been given to the production of fertilizers that have low initial solubility and release nutrients to the soil and plant gradually over an extended period of time.

This is a list of commonly used fertilizers with their nitrogen, Phosphate or potassium contents:

ammonium sulfate (21% N) N=Nitrogen
ammonium nitrate (35% N)
muriate of potash (50% K) K=Kalium or Potassium
urea (46% N)
sulfate of potash (45% K)
anhydrous ammonia (82% N)
diammonium phosphate (21% N, 23% P) P=Phosphor
monoammonium phosphate (12% N, 27% P)
superphosphate (9% P)
superphosphate (21% P)

Question/ Purpose:

What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.

Problem statement: High cost of fertilizers is a major problem for many farmers and producers of different plants. By identifying different materials that can be used as fertilizers we may be able to find some free or low cost fertilizers. For example we may discover certain household or industrial waste materials that are good fertilizers and are widely available at no or little cost.

Question: Any of the following questions can be used for this project.

  • What material are fertilizers?
  • What chemical elements play a major roll in fertilizers?
  • What household waste can be used as fertilizer?
  • Compare 5 materials (of your choice or assigned by teacher) to see which one is a better fertilizers.
  • Compare different types of fertilizers for one specific plant to see which combination produces the best result?

If the question that you have selected is not listed above, consult with your project advisor.

Identify Variables:

When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.

Independent (manipulated) variables for testing fertilizers are usually the amount and the type of fertilizer. In some tests, instead of amount of fertilizer, you may consider only the amount of active elements of that fertilizer. For example amount of nitrogen may be considered as variable, not the amount of a nitrogen based fertilizer. The reason is that some fertilizers have more nitrogen than others.

This is a sample on how you may define your variables:

  • Independent variable (also known as manipulated variable) is the type of fertilizer. Possible values are Miracle-Gro, Ground coffee beans, egg shell, meat, rice or any other substances that you may want to test their effects as a fertilizer.
  • Dependent variable is the plant growth.
  • Constants are the plant type, plant age, soil type, the amount of soil, and the amount of water.
  • Controlled variables are light, temperature and other environmental conditions. We make sure that all our test plants grow under the same light and temperature conditions.


Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis.

This is a sample hypothesis for comparing Miracle gro, Ground coffee beans, egg shell, meat and rice as fertilizers:

Miracle grow is a mixture of known inorganic fertilizers, so it must produce the best results.

Ground coffee contains some soluble material and is part of another plant with some organic contents, so it might contain some nutrition for plants.

Egg shell is not water soluble and does not easily decompose, so it must have no effect.

Meat is a protein with high level of nitrogen contents, but maybe it does not decompose fast enough to show any result for our 10 day experiment.

Rice is a carbohydrate (mostly starch) that does not contain any of fertilizer elements. Therefore it must be as bad as the egg shell.

Experiment Design:

Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”

Introduction: A general and simple method for testing fertilizers is using small pots and identical plants. All physical and environmental conditions for all sample plants must remain the same and the only variable will be the type or the amount of fertilizer that you add.


  1. Obtain/ purchas six identical, same size, same type young plants for your experiment. Alternatively you may decide to start by planting seeds. If you plant your own seeds, your experiment takes about 4 to six more weeks to complete. In any case you need good weather and enough light for your plant experiments. If you start by planting seeds, use only top spoil in your flower pots. Do not use potting soil because it already contains a lot of organic mater and some fertilizers.

Fill up half of the pot with soil, place 3 seeds in each pot and then cover them with additional one inch soil. Give equal amount of water to all pots.

  1. Each pot will be used for testing one fertilizer, so label each pot with the name of fertilizer you are planning to add to that pot. Label one of the pots as “Control”, this pot will not get any fertilizer.
  2. Since you are comparing different fertilizers, you can add a certain weight of each fertilizer. For example you may add 5 grams of dry ground meat in one pot, 5 grams of ground coffee beans in second pot, 5 grams of egg shell in the third pot, five grams of rice in the fourth pot and five grams of Miracle-Gro in the last pot. Mix the fertilizer with the upper layer of the soil. When you water the plant, water will transfer nutrients down to other parts of the soil.
  3. Water the plants daily and make daily observations.

At the end either visually or by other methods such as weight or height of plant you grade each fertilizer based on its effects.

How long does it take?

You may continue your experiment for a certain amount of time (2 months for example), or you may continue it until you see a clear difference between the growth rate of different plants.


If you think there are other materials around you that may be a fertilizer for plants, feel free to test them. Just make sure that you grind everything and mix it with the upper layer of the soil. Also, try to use dry material or adjust their amount to compensate for their water content. For example you may think that a banana skin may be a good fertilizer, but more than 80% of banana skin is water, therefore you use 25 grams of fresh banana skin instead of 10 grams of dry banana skin. You may do the same for ground meat. Meat usually has about 75% water, so if you don’t have dry meat, use 20 grams of fresh ground meat for it’s 5 grams contents of dry meat.

Make your results more reliable:

You may want to use 3 identical plants for each fertilizer and 3 of the same plant for control in order to have a more reliable result.

Materials and Equipment:

Material and equipment needed for such experiments are:

  • Ceramic pots
  • Inexpensive and unfertilized potting soil for the test
  • (Optional) Soil pH tester to make sure all soil samples have the same pH
  • Identical young plants or some fast growing seeds

Results of Experiment (Observation):

During test period you make daily observations and record the results similar to the following:

This is the result of growth comparison test between three fertilizer brands (MicroMagic, Miracle Gro, Medina and Peters Professional). The test focused on total plant growth in height per test pot; number of beans that germinate in each pot; leaf size comparison, comparison of root growth per test pot; and price comparison to the three other organic products.

Six test pots were used. Three of the pots were treated with MicroMagic, (two with 25% nitrogen added, and one with ONLY MicroMagic). The other three pots were each treated with Miracle Gro, Medina, and Peters Professional. The appropriate amount of each product was added to the tests pots, relative to the directions on each of the products. Four beans were placed in each test pot. (Test period is 10 days).

DAY 2 – There were only three pots with sprouts showing and THEY WERE ALL THE MicroMagic PLANTS. This shows how much faster germination occurs with MicroMagic.

DAY 5 – There were only 4 test pots with any significant growth. The three MicroMagic test pots had a total of 10 plants, six of which were 5″ and more. Of the three other products, the Medina, had one short plant, and one sprout; the Miracle Gro had only 1 sprout; and the Peters had only a short plant and two sprouts.

DAY 7 – The MicroMagic Pot #1 (with 25% added fertilizer) had 3 plants with a total of 19.75 inches of growth. MicroMagic Pot #2 (with 25% added fertilizer) had 3 plants with a total of 17.5 inches of growth. The MicroMagic Pot #3 (with NOTHING ADDED) had 4 plants with a total of 29.25 inches of total growth. The Medina had 3 plants with 15 inches of total growth. The Peters had 2 plants with a total of 10 inches total growth, and the Miracle Gro only had one small plant 3.5 inches tall. THE TOTAL GROWTH OF THE THREE MicroMagic TEST POTS, IN ONLY 7 DAYS, WAS 66.5 INCHES. The total growth of the other three test products was only 28.5 inches. A difference of 38 inches!

DAY 10 – CONCLUSION OF THE TEST: The total growth of the MicroMagic test pots was 118.75 inches. The total growth of the three other test products was only 50.75 inches. This is a difference of 68 inches in only 10 days of testing.
As you can see by the attached pictures, the MicroMagic was substantially better in all aspects of the test’s purpose. The photograph has the MicroMagic plants lined up on the left, and the other three test pots on the right. The next picture shows all of the leaves that were removed from the test pots. The left side MicroMagic leaves are the larger and more numerous compared to the other test products on the right. The third picture shows the root structure of the three MicroMagic test pots on the left and the three others on the right. In the fourth picture, the plants were separated in each pot to show the individual difference in the root growths, The MicroMagic shows far more advanced root systems in only 10 days.

After completion of the test period (for example 10 days), record the final results in a table similar to this:

 Visual grade  Height grade  weight grade  fruit amount
+ 25% Nitrogen
+ 25% Nitrogen
 Miracle Gro
Medina and
 Peters Professional

Fruit amount is used only if you grow a plant that has fruit such as tomato.

Summary of Results:

Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during the experiments.


Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.

Related Questions & Answers:

What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.

Possible Errors:

If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.

If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.


List of References:

Fertilizer Zone

Fertilizer Basics

This information is extracted from Fertilizer Zone, visit that for more info: http://cumberland.ces.state.nc.us/fertpage/fertmain.html

Why do we need fertilizer?

Plants require 16 nutrients for optimum growth. Often, the soil doesn’t hold enough of these nutrients in the quantities needed for desirable growth and production. The nutrients, that are in the soil, are often used up and need to be replaced.

Nutrients, such as nitrogen, are easily leached by water and can also be volatilized into the atmosphere. These nutrients are usually not available, in sufficient quantities, from the soil. Therefore, we need to add extra plant nutrients to the soil ( or in some cases, on plant foliage ) to obtain maximum plant performance. We add these nutrients by applying fertilizer. For more information about the nutrients required by plants, see the article “Essential Plant Nutrients”.

What is fertilizer?

Fertilizer is any material that supplies one or more of the essential nutrients to plants. Fertilizers can be classified into one of two categories: organic or inorganic. Organic fertilizers are derived from living or once living material. These materials include animal wastes, crop residues, compost and numerous other byproducts of living organisms. Inorganic fertilizers are derived from non-living sources and include most of our man-made, commercial fertilizers. For more information about both categories of fertilizers, see the articles “Organic Fertilizer Sources” and “Inorganic Fertilizer Sources”.

What kind of fertilizer should I use?

Several considerations should be made before deciding on a fertilizer choice. First of all, you need to consider the nutritional needs of the crop for optimum performance. Secondly, you need to have you soil analyzed to see what is available in the soil. After you know what your crop needs and what is available in the soil, you can determine the nutrients and the amounts that you need to add to the soil.

The amount of each nutrient, that you need to add to the soil, will determine your choice of fertilizer. Choose the one that best matches your needs. You may find that you will need to use two or more types because one type may not satisfy all of you crops needs.

As for organic verses inorganic types, both have their advantages and disadvantages. Inorganic types are easier to use and we have more control over the content of nutrients in these sources. This allows us to apply our nutrients more accurately.

Organic sources are variable in their nutrient content and we have very little control over this. However, organic sources can sometimes be obtained for little or no cost, it adds valuable organic matter to the soil and has some slow release action. Again, for more detailed information about each of these fertilizer sources, see the articles “Organic Fertilizer Sources” and “Inorganic Fertilizer Sources”.

When should I apply my fertilizer?

Timing means everything to the efficient use of fertilizer. As a rule of thumb for all plants, fertilizer needs to be applied when the plant is actively growing. This timing will depend on the specific crop that you are growing. Before applying, know when your crop needs fertilizer and apply it so that the nutrients will be available when the plants need them.

How much fertilizer do I need to apply?

Just as I mentioned earlier for determining the type of fertilizer to use, you will need to know your crop needs as well as the amount of nutrients available in the soil, to determine the amount of fertilizer to apply. Find out what your crop needs and have your soil tested. Then apply the amount of fertilizer that you need to make up for the deficit in the soil. For more information about soil testing, see the articles “Careful Soil Sampling” and “Understanding Your Soil Test Report”.

How do I apply my fertilizer?

The method of fertilizer application will depend on the type of fertilizer that you use. Granular types can be applied by hand or with spreading equipment and some can be dissolved in water, sprayed on the foliage or applied through the irrigation system. Most organic sources will need to be spread by hand or with some kind of specialized equipment. It is also a good idea to incorporate both organic and inorganic sources into the soil to prevent the loss of nutrients through volatilization and erosion.