Which Fertilizer Works Best for Radish Plant Growth?

Researched by Jacob Z.


The purpose of this experiment was to determine which brand of store bought fertilizer works best for radish plant height and biomass.

I became interested in this idea when my family started a garden and I just wanted to find out which fertilizer works best. 

The information gained from this experiment will help home gardeners and commercial farmers know which fertilizer works the best for radish plant growth.

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My hypothesis is that Miracle Grow will work the best for radish plant height and biomass.

I base my hypothesis on information I collected while doing research on the minerals that plants need to grow healthy and strong.  Miracle grow has many of these minerals which helps plants grow tall and healthy.
Nitrogen, phosphorous, potassium, calcium, magnesium, sulfur, iron, boron, manganese, copper, zinc, molybdenum, chlorine, and nickel. I learned this while reading "World Book Encyclopedia."and Plant Biology Science Projects.


The constants in this study were: 

  • The type of plant.
  • The amount of water.
  • How often watered.
  • The environment grown in (light, temperature, wind, etc.).
  • The amount of fertilizer.
  • The size of holding cell.
  • The number of seeds in holding cell.

The manipulated variable was the brand of fertilizer. 

The responding variable was the height and biomass of the radish plant. 

To measure the responding variable I used a ruler and a triple beam balance. 

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1 Bag of potting soil
Bag of Miracle Grow fertilizer20-20-20 %20 nitrogen %20 phosphoric acid %20 soluble potash.
1 Bag of  Peters fertilizer20-15-25 %20nitrogen %15 phosphoric acid %25 soluble potash.
1 Bag of Schultz fertilizer20-30-20 %20nitrogen %30 phosphoric acid %20 soluble potash.
Measuring cup
1 Fluorescent light source
72 plant holding cells
1 6 ft. extension cord


1. Fill holding cells to top with potting soil. 
2. Moisten potting soil with warm water.
3. Put 2 radish seeds in each container 1 in each corner. 
4. Mix each fertilizer into 1-gallon containers of water, according to manufacturer instructions. 
5. Pour 2ml of mixture into measuring cup for each square holding cell
6. Repeat step 5 with other 2 fertilizers.
7. Water control group with 2ml of water.
8. Place each group of holding cells in a plastic container.
9. Hang light from shelf.
10. Place trays and holding cells on shelf.
11. Set timer on light.
12. Measure plants weekly
13. Water plants daily.
14. Fertilize according to manufacturer instructions.
15. Repeat steps 12 through 14 until plants are ready to be picked.
16. When plants are full grown and ready to be picked pick each plant.
17. Measure plants from leaves to bottom of roots.
18. Weigh each plant on triple beam balance.
19. Record results.
20. Repeat steps 16 through 19 with all other plants in group holding cell.
21. Average results.
22. Repeat steps 20 and 21 with other two fertilizer groups and control.


The original purpose of this experiment was to determine which brand of fertilizer works best on radish plant height and biomass.

The results of the experiment were that for height Schultz fertilizer was the tallest with an average height of 9.82cm, Peters was second with and average height of 9.69cm, and Miracle Grow was third with an average height of 8.88cm, and the control was last with an average height of 8.25cm. For biomass, Schultz fertilizer was first with 9.4g, Miracle Grow was second with 8.1g, Peters was third with 7.9g, and control was last with 7.7g. 

See the table and graph.


My hypothesis was that Miracle Grow would work the best for both height and biomass. 

The results indicate that this hypothesis 1 (height of plant) should be rejected and my hypothesis 2 (biomass) should be rejected.

Because of the results of this experiment, I wonder if I should have given the plants more fertilizer and a longer grow time.

If I were to conduct this project again I would use more types of fertilizer, different types of fertilizer, and a larger group of each fertilizer.

Plants have to be one of our most important resources. They account for more than half of our food supply, plants and trees contribute to our clean air, plants are responsible for cleaning our water, plants and trees provide shade and protection for people, and plants account for most of our medicines and vaccines. No matter where you look plants are everywhere. Without plants no one would be able to live on earth and farmers wouldn’t have a job. Plants help keep the ozone layer from deteriorating and breaking apart and reducing radiation from reaching the earth and ruining farmers’ crops and causing skin cancer. Without plants our planet would eventually turn into a dead unlivable place with no life.

 Fertilizers provide plants with nutrients, macronutrients, and micronutrients that are essential for a plant to grow tall, strong, and healthy. The three numbers on the side of a bag of fertilizer stands for the percent of nitrogen, phosphoric acid, and soluble potash contained in that bag of fertilizer. Fertilizers come in many forms such as powder (which is used as a mixture in water), stakes (that you stick in the ground), and solids, which you sprinkle around the plant. A fertilizer is defined as a material that contains one or more of the mineral nutrients required by plants. There are six macronutrients. They are nitrogen, phosphorous, potassium, calcium, magnesium, and sulfur. The eight micronutrients are iron, boron, manganese, copper, zinc, molybdenum, chlorine, and nickel. The more of these nutrients a plant is allowed generally the stronger and healthier that the plant and fruits and vegetables will grow.

There are many parts to plants including the leaves, the stem, and the roots. Then there are more specific parts of a plant that perform more complicated jobs such as the reproductive parts, which produce seeds. The roots absorb water and nutrients that are essential to a plants' survival and growth. In such plants as radishes, potatoes, and carrots the vegetable is the root. The stem acts as a straw to carry the water and nutrients to the other parts of the plant such as the leaves. On fruit and other above ground plants the stem carries the water and nutrients to the fruit or vegetables also.  The leaves suck in the water from the stem and turns it into food by a process called photosynthesis, which is the caused by the sun hitting the water stored in the "sponge" like leaves. 
The light converts the energy into several forms. The first step is the conversion of a photon into an electronic state of an electronic pigment located in the antenna system. The antenna system is made up of hundreds of pigment molecules that are attached to proteins with photosynthetic membranes and serve as a special protein complex, which is Known as a reaction center. Then the electronic state is transferred to the antenna molecules as an exciton. If an exiton gets trapped then one of three things happen to it. Some are converted back into photons and emitted as fluorescence, some are converted to heat, and some are trapped in a reaction center protein. If they are trapped in a reaction center protein then they are used to perform the main process of photosynthesis, which is the transfer form a donor molecule to an acceptor molecule. Both of which are attached to the reaction center. Once charge separation happens electron transfer reactions are energetically downhill. The pigment found in plants known as chlorophyll gives plants their green color and absorbs the light essential for this process. 
 Without any of these parts of the plant the plant could not survive.

 There are generally two types of soils that a gardener uses: ground soil and potting soil. Potting soil is more effective because it is much more porous than regular ground soil and can hold more water and nutrients. A problem with potting soil is that you can not pack it or it will not hold very much water or nutrients and the plant will not grow as well. The best way to place the potting soil into a container is to just pour it in and gently tap the pot on the ground or to lightly smooth it out with your hand. To moisten the soil you should use warm water instead of cold water because warm water will soak in while cold water will just stick to the top of the soil and will not soak in. For a plant to grow the soil will need to always be damp or the plant will wither up and die. Some potting soils are more porous and need more water to moisten them for the first time but don't need as much to keep them moist so they do not need to be watered as often.

 There are different types of light sources. There is sunlight and artificial light. Light is essential for a plant to perform the process called photosynthesis (look at "Plant Parts"). The sunlight emits a type of light called ultraviolet. Ultra violet light is the light that plants use to perform the process called photosynthesis, which is the transformation of light energy into food for the plant. Artificial light gives off much of the same light but does not give off the heat that will dehydrate a plant and maybe even burn the plant or the fruits or vegetables on the plant. There are other advantages of having artificial light rather than sunlight which are that you can grow plants all year round, you do not have to worry about the sun not coming out because the plants will always have light, and that plants are out of the weather such as wind, snow, rain, cold weather, and extremely hot and dry weather. Most plants could germinate but could not live in an environment with no light.

 Plants are essential to our survival. Plants provide us with food, they provide us with clean water, they provide us with clean air, they prevent landslides, and provide us with medicines and herbs. Plants also protect the ozone from dissolving and letting radiation from the sun kill the plants and even people. Some people don't realize it but if you took away plants then the entire world would perish. That is why plants are one of the most important organisms on earth.

Smith, Steve W. www.plants.com downloaded 12-10-2000

Plants "World Book Encyclopedia" 1999 pg.516-545

Hershey, David R. "Plant Biology Science Projects." John Wiley & Sons, inc. Toronto 1995 

Fertilizer "New Book of Knowledge" 1998 Aaron Sampson publishing. New York. pg. 220-224

"Soils and Fertilizer", www.ask.com/plants/soils/fertilizer. Downloaded 12-27-2000

"Photosynthesis", http://encarta.msn.com/find/concise.asp?ti=029A9000. Downloaded 1-15-2001


I would like to thank the following people for helping me with creating my science project and experiment.

  •  I would like to thank my family for encouraging me to do anything that I put my mind to.
  • Last, but not least, I would like to thank Mr. Newkirk for going out of his way to find me radish seeds in the middle of the winter, finding me a grow light and timer, and for staying after school until 6 p.m. so many days so that I could finish my project.

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