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Determine the effects of various nutrients on plant growth

Determine the effects of various nutrients on plant growth

Introduction: (Initial Observation)

Plants need water, nutrients and proper environmental conditions in order to grow. Without these elements no plant will survive, grow or reproduce. Plants get their nutrients from soil or any other medium surrounding the root.

For many years human has learned the animal droppings are fertilizers (contain nutrients) and cause the plants grow faster, bigger or taller. They have also learned that burying dead animals next to a tree results a faster growth and more fruit on trees.

During the long history of agriculture, human has learned about many organic and inorganic material that can help plant growth. Such material contain nutrients that plants need for their cells. With today’s knowledge of chemistry we know about these nutrients and their sources. This knowledge has also helped human to mass produce synthetic fertilizers.

In this project we will try to see the effect of various nutrients on plant growth.


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 nutrients for plants. 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.


Plant Nutrients


Sixteen chemical elements are known to be important to a plant’s growth and survival. The sixteen chemical elements are divided into two main groups: non-mineral and mineral.

Non-Mineral Nutrients

The Non-Mineral Nutrients are hydrogen (H), oxygen (O), & carbon (C).

These nutrients are found in the air and water.

In a process called photosynthesis, plants use energy from the sun to change carbon dioxide (CO2 – carbon and oxygen) and water (H2O- hydrogen and oxygen) into starches and sugars. These starches and sugars are the plant’s food.

Photosynthesis means “making things with light”.

Since plants get carbon, hydrogen, and oxygen from the air and water, there is little farmers and gardeners can do to control how much of these nutrients a plant can use.

Mineral Nutrients

The 13 mineral nutrients, which come from the soil, are dissolved in water and absorbed through a plant’s roots. There are not always enough of these nutrients in the soil for a plant to grow healthy. This is why many farmers and gardeners use fertilizers to add the nutrients to the soil.

The mineral nutrients are divided into two groups:
macronutrients and micronutrients.


Macronutrients can be broken into two more groups:
primary and secondary nutrients.

The primary nutrients are nitrogen (N), phosphorus (P), and potassium (K). These major nutrients usually are lacking from the soil first because plants use large amounts for their growth and survival.

The secondary nutrients are calcium (Ca), magnesium (Mg), and sulfur (S). There are usually enough of these nutrients in the soil so fertilization is not always needed. Also, large amounts of Calcium and Magnesium are added when lime is applied to acidic soils. Sulfur is usually found in sufficient amounts from the slow decomposition of soil organic matter, an important reason for not throwing out grass clippings and leaves.


Micronutrients are those elements essential for plant growth which are needed in only very small (micro) quantities . These elements are sometimes called minor elements or trace elements, but use of the term micronutrient is encouraged by the American Society of Agronomy and the Soil Science Society of America. The micronutrients are boron (B), copper (Cu), iron (Fe), chloride (Cl), manganese (Mn), molybdenum (Mo) and zinc (Zn). Recycling organic matter such as grass clippings and tree leaves is an excellent way of providing micronutrients (as well as macronutrients) to growing plants.


In general, most plants grow by absorbing nutrients from the soil. Their ability to do this depends on the nature of the soil. Depending on its location, a soil contains some combination of sand, silt, clay, and organic matter. The makeup of a soil (soil texture) and its acidity (pH) determine the extent to which nutrients are available to plants.

Soil Texture

(the amount of sand, silt, clay, and organic matter in the soil)

Soil texture affects how well nutrients and water are retained in the soil. Clays and organic soils hold nutrients and water much better than sandy soils. As water drains from sandy soils, it often carries nutrients along with it. This condition is called leaching. When nutrients leach into the soil, they are not available for plants to use.

An ideal soil contains equivalent portions of sand, silt, clay, and organic matter. Soils across North Carolina vary in their texture and nutrient content, which makes some soils more productive than others. Sometimes, the nutrients that plants need occur naturally in the soil. Other times, they must be added to the soil as lime or fertilizer.

Soil pH

(a measure of the acidity or alkalinity of the soil)

Soil pH is one of the most important soil properties that affects the availability of nutrients.

  • Macronutrients tend to be less available in soils with low pH.
  • Micronutrients tend to be less available in soils with high pH.

Lime can be added to the soil to make it less sour (acid) and also supplies calcium and magnesium for plants to use. Lime also raises the pH to the desired range of 6.0 to 6.5.

In this pH range, nutrients are more readily available to plants, and microbial populations in the soil increase. Microbes convert nitrogen and sulfur to forms that plants can use. Lime also enhances the physical properties of the soil that promote water and air movement.


Nitrogen (N)

  • Nitrogen is a part of all living cells and is a necessary part of all proteins, enzymes and metabolic processes involved in the synthesis and transfer of energy.
  • Nitrogen is a part of chlorophyll, the green pigment of the plant that is responsible for photosynthesis.
  • Helps plants with rapid growth, increasing seed and fruit production and improving the quality of leaf and forage crops.
  • Nitrogen often comes from fertilizer application and from the air (legumes get their N from the atmosphere, water or rainfall contributes very little nitrogen)

Phosphorus (P)

  • Like nitrogen, phosphorus (P) is an essential part of the process of photosynthesis.
  • Involved in the formation of all oils, sugars, starches, etc.
  • Helps with the transformation of solar energy into chemical energy; proper plant maturation; withstanding stress.
  • Effects rapid growth.
  • Encourages blooming and root growth.
  • Phosphorus often comes from fertilizer, bone meal, and superphosphate.

Potassium (K)

  • Potassium is absorbed by plants in larger amounts than any other mineral element except nitrogen and, in some cases, calcium.
  • Helps in the building of protein, photosynthesis, fruit quality and reduction of diseases.
  • Potassium is supplied to plants by soil minerals, organic materials, and fertilizer.

Calcium (Ca)

  • Calcium, an essential part of plant cell wall structure, provides for normal transport and retention of other elements as well as strength in the plant. It is also thought to counteract the effect of alkali salts and organic acids within a plant.
  • Sources of calcium are dolomitic lime, gypsum, and superphosphate.

Magnesium (Mg)

  • Magnesium is part of the chlorophyll in all green plants and essential for photosynthesis. It also helps activate many plant enzymes needed for growth.
  • Soil minerals, organic material, fertilizers, and dolomitic limestone are sources of magnesium for plants.

Sulfur (S)

  • Essential plant food for production of protein.
  • Promotes activity and development of enzymes and vitamins.
  • Helps in chlorophyll formation.
  • Improves root growth and seed production.
  • Helps with vigorous plant growth and resistance to cold.
  • Sulfur may be supplied to the soil from rainwater. It is also added in some fertilizers as an impurity, especially the lower grade fertilizers. The use of gypsum also increases soil sulfur levels.


Boron (B)

  • Helps in the use of nutrients and regulates other nutrients.
  • Aids production of sugar and carbohydrates.
  • Essential for seed and fruit development.
  • Sources of boron are organic matter and borax

Copper (Cu)

  • Important for reproductive growth.
  • Aids in root metabolism and helps in the utilization of proteins.

Chloride (Cl)

  • Aids plant metabolism.
  • Chloride is found in the soil.

Iron (Fe)

  • Essential for formation of chlorophyll.
  • Sources of iron are the soil, iron sulfate, iron chelate.

Manganese (Mn)

  • Functions with enzyme systems involved in breakdown of carbohydrates, and nitrogen metabolism.
  • Soil is a source of manganese.

Molybdenum (Mo)

  • Helps in the use of nitrogen
  • Soil is a source of molybdenum.

Zinc (Zn)

  • Essential for the transformation of carbohydrates.
  • Regulates consumption of sugars.
  • Part of the enzyme systems which regulate plant growth.
  • Sources of zinc are soil, zinc oxide, zinc sulfate, zinc chelate.

Silt refers to soil or rock particles of a certain very small size range (see grain size). On the Wentworth scale, silt particles fall between 1⁄256 and 1⁄16 mm (3.9 to 62.5 μm), larger than clay but smaller than a sand.

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.

The purpose of this project is to determine the effect of various nutrients on plant growth (i.e. plant height, stem volume).

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.

We change the types of nutrient (independent variable) to see how does this affect the plant growth (dependent variable).

Independent variable (also known as manipulated variable) is the type of nutrient. Possible values (to choose from) are:

  • Ammonium nitrate (a source of nitrogen) or ammonium sulfate
  • Calcium phosphate (a source of phosphors)
  • Potassium nitrate (a source of potassium and nitrogen)
  • Potassium Sulfate (a source of potassium)
  • Magnesium sulfate (a source of magnesium)
  • Ammonium phosphate (a source of nitrogen and phosphors)

Dependent variable is the rate of plant growth. Plant growth can be determined by the plant height, number of leafs, size of leafs.

Constants are the type of seed, the amount of water, the amount of nutrients.

Controlled variables are light and temperature.

Trouble finding nutrients?

You may perform the same experiment using commercially available fertilizers that are a mixture of multiple nutrients. You may even try household items such as detergents, tea, coffee, crushed chicken bone or juices to see if they can work as a nutrients for plants.


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.

My hypothesis is that a proper mix of various nutrients will result the highest growth in plant.

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.”

In order to test the effect of various nutrients on plant growth, we plant some seeds and use them to test the effect of different nutrients.

Materials: radish seeds (one packages will be enough for multiple experiments), water, paper towels, plastic beverage cups, aluminum foil, samples of liquid fertilizers (plant food purchased from the grocery or home supply store)


  • Soak the radish seeds in water for about an hour. (Some seeds such as lentil may be soaked for 24 hours)
  • Fold a paper towel lengthwise and float it in a shallow pan of water. Remove it and gently wring out the excess water.
  • Get 6 soaked radish seeds
  • Lay the soaked seeds along the folded edge of the moist paper towel. Roll the paper with the seeds into a cylinder, as in the diagram.
  • Repeat with the above steps four times until you have four rolled paper towel with 6 seeds in each of them.
  • Place the rolled paper cylinders in separate plastic beverage cups and add water to each cup to a depth of 2-3 cm.
  • Label one of the cups as a control and label the others with the type or name of fertilizer (nutrient) that you are going to use.
  • Provide nutrients to the experimental cup by adding a couple of drops of liquid fertilizer to the water.
  • Place a piece of aluminum foil loosely over all four cups and allow the cups to remain undisturbed until the seeds germinate (2 to 4 days). During this time enough moisture must be available to the seeds.
  • Once the seeds have germinated, remove the foil and place the cups in a location that provides them with light.
  • Measure the roots and the shoots of the growing plants and chart the growth of their seedlings every day or two.
  • Describe the effect of additional nutrients on the growth of the seedlings.

Above description is for testing 3 different types of nutrients. If you want to test more then 3 or if you want to repeat the experiments with different amounts of nutrients, you will need to prepare more cups with the same way.

The reason that we place 6 seeds in each paper towel is to see the average result, not the result of an accidentally large seed.

Materials and Equipment:

  • Radish seeds (one packages will be enough for multiple experiments)
  • Water
  • Paper towels
  • Plastic beverage cups
  • Aluminum foil
  • Samples of liquid fertilizers (plant food purchased from the grocery or home supply store)
  • Sample of other material that you may want to test as nutrients such as sugar, urine, milk.

If you get any solid fertilizer for test, first dissolve them in water and then use a few drops for test.

Results of Experiment (Observation):

Record the results of your experiments in tables like this:

This table shows the average height of seedlings in each cup in different days.

Water only

Nutrition 1

Nutrition 2

Nutrition 3

Day 1
Day 2
Day 3
Day 4
Day 5

Questions for Students:

1) Why did you need four cups to perform this experiment? What conclusion could you draw if you had performed the experiment with only one cup?

2) What effect did the fertilizer have on the plant growth?

3) If you put in twice as much fertilizer, what effect would this have on the plant growth? How could you find out?

4) How does this experiment relate to human nutrition?


You may need to calculate the average heights of seedlings in each paper towel.

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 experiments.

It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.


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.


Find and review some books about plants, nutrients and fertilizers.