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Roots – how do different types of soils affect the ability of roots to anchor plants?

Roots - how do different types of soils affect the ability of roots to anchor plants?

Introduction: (Initial Observation)

Plant roots are mainly used to absorb water and nutrients that the plant needs for growth. It is important for the root to stay in the ground where water and nutrients are available. It is also important for most plants to stay in an upward position.

Plant roots have a secondary role that is anchoring the plant in the soil, keeping it in an upward steady position and protecting it against natural phenomena such as wind and rain that may force the plant out of the soil. In this project we will test to see how the type of soil affects the plants’ root ability to anchor the plant.


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 plant roots and different types of soil. Read books, magazines or ask professionals who might know in order to learn about soil classification and the effects of soil type on plants. Keep track of where you got your information from.

How many soils are there?

Sand, silt, and clay are the basic types of soil. Most soils are made up of a combination of the three. The texture of the soil, how it looks and feels, depends upon the amount of each one in that particular soil. The exact proportions of each of these three constituents may vary, and as they do the soil type changes. The type of soil varies from place to place on our planet and can even vary from one place to another in your own backyard.

A soil ‘texture triangle’ can be used to describe textual soil types with more precision. Sand particles are sized from 2mm to 0.06mm, silt soils are sized from 0.06mm to 0.002mm and clay particles are less than 0.002mm in size.

Loam is soil composed of a mixture of sand, clay, silt, and organic matter.

Visit Soil Composition for more information about soil elements.


Often roots are overlooked, probably because they are less visible than the rest of the plant. However, it’s important to understand plant root systems because they have a pronounced effect on a plant’s size and vigor, method of propagation, adaptation to soil types, and response to cultural practices and irrigation.

Roots typically originate from the lower portion of a plant or cutting. They have a root cap, but lack nodes and never bear leaves or flowers directly. Their principal functions are to absorb nutrients and moisture, anchor the plant in the soil, support the stem, and store food. In some plants, they can be used for propagation.

Ideal Soil:

An ideal soil is about 50 percent solid material, consisting mainly of minerals and a small percentage of organic matter. The other 50 percent of this ideal soil is pore space, which consists of small holes between soil particles that are filled with water and air in different amounts. After rain or irrigation, the pores may be nearly filled with water and the air is pushed out. As the soil dries, the amount of water decreases and the pores gradually fill with air again. The ideal water-to-air ratio in the pores is about half and half, 50 percent air to 50 percent water.

The amount of moisture and air a soil holds depends on the soil structure and the type of soil. Sandy soils with large particles have large pore spaces. Pore space can be illustrated by comparing a door or window screen to nylon stockings. The screen represents the large pore spaces found in sandy soil, and the nylon represents clay soil with small pore spaces. If you dip each into water, you can observe the differences in the two as to how they hold water. Water is lost more quickly from these large pores as the force of gravity drains the water out; these are well-drained soils. As the content of clay in the soil increases, more water is held. If soils contain too much clay, they may not drain well enough to allow enough oxygen in the pore space for good plant growth.


Soil Types:

SANDY SOIL: Sandy (or light) soils are soils in which silt and clay make up less than 20 percent of the material by weight. These soils drain well, but have little capacity to hold moisture and plant food. Sandy soils have comparatively large particles that permit good aeration, quick passage of water, and quick warming.

CLAYEY SOIL: A clayey soil must contain at least 30 percent clay and is known as a heavy soil. Heavy soils have relatively poor drainage and aeration capabilities. Because of this, heavy soils tend to hold more moisture than is good for plants. However, this type of soil also holds fertilizer and plant food well, which can be beneficial to plant growth.

LOAMY SOIL: This is the most desirable soil for agricultural use. Loam is a mixture of approximately equal parts of sand, silt, and clay. If the loamy soil has more sand than silt or clay, it is known as a sandy loam; more clay, it is known as a clayey loam; more silt, a silty loam.

Learning Activities

To experience a realistic examples of the differences between clayey, sandy, and loamy soils, try the following activity.

Activity 1
What you will need:

    • 1 cup of sugar/salt
    • 1 cup of flour
    • modeling clay
    • 1 cup of water

What you will do:

  1. Rub sugar or salt between your thumb and finger to give you an idea of what sand feels like.
  2. Add a few drops of water to the sugar or salt. Describe how it feels. Do the crystals stick together?
  3. Feel some flour between your fingers. Describe how it feels. This is the way silt feels.
  4. Add a few drops of water to the flour. How does it feel now? Does it stick together?
  5. Feel the modeling clay. This is how clay in the soil feels.
  6. Add a few drops of water to the clay. How does it feel now? Is there any difference?


The Textural Triangle

A triangle can be used to determine the textural name of a soil by actually measuring the percentage of sand, silt, and clay found in the soil. After the percentages of silt and clay are determined, these amounts can be plotted on the textural triangle. To do this, project lines inward from the point on each side of the triangle that represents the percentage of that particular type of soil. The line drawn from the silt side of the triangle is placed parallel to the sand side of the triangle. The line projected from the clay line runs parallel to the silt line. The location of the point at which these two lines intersect indicates the name of the soil. The name of the section of the triangle in which the point is located is the name of the soil.

Using the Textural Triangle, determine what soil type was used in the experiment.

HINT (Sand is heavier than clay, which is heavier than silt.)

Explain how you determined this.

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 question is: How do different types of soils affect the ability of roots to anchor plants?

The results of this project may help us to improve the quality of any soil by mixing it with other specific types of soil.

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 variable (also known as manipulated variable) is the combination of the soil (percent of sand or percent of clay in the soil).

Dependent variable (also known as responding variable) is the force required to uproot the plant.

Constants are the water ratio, preparation method and experiment method.

Controlled variables are weather temperature and moisture.


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.

Following is a sample hypothesis.

Among the soil components, clay has the highest adherence. That is why clay is used as binding material in construction, sculpture and ceramics.

My hypothesis is that the ability of roots to anchor plants increase by any increase in the amount of clay in the soil.

This hypothesis is being tested in experiments number 4 and 5.

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.”

Experiment 1:

Taking a soil sample


10″ piece of PVC pipe, 1″ diameter
wooden block
10″ piece of dowel that fits inside the PVC pipe
white paper
pencil, colored pencils
magnifying glass
plastic knife
zip-lock bags


1. Select a soil sampling sight. Place one end of the PVC pipe on the ground. Place the wooden block on top and carefully pound the pipe into the soil using a hammer. For safety, wear a work glove on the hand that holds the pipe. Pound it in until about 4″ are sticking out of the ground.

2. Grab the pipe and twirl it gently in a circle to loosen it up. Tap it on the sides with hammer if necessary. Then carefully pull the pipe out, making sure the soil is still inside.

3. Push the soil out carefully with a dowel. Make sure to lay the soil on a flat surface. White paper works well.

4. Without breaking it, observe the soil very closely. Pay close attention and jot down anything you find interesting.

    • How is the top part of the soil different from the bottom?
    • Does the color change along the surface of the soil?
    • Do you see layers of different types of soil?
    • What can you observe about the soil?
    • Is anything living in the soil?

5. Draw a look-a-like picture of your soil sample. Make sure you draw what you find out. Use colors and label anything interesting.

6. Once you are satisfied with your drawing you can then estimate more. Cut the soil sample down the middle lengthwise with a plastic knife. Look inside. Note anything interesting.

7. Look at the different things using a magnifying glass.

8. Carefully pull it apart. Separate the soil’s different parts into categories. You are probably going to find three or four groups. You may find more.

9. Place categories in the plastic bags. You may now make a display for others. Tape the bags around your picture. You can now draw arrows to that part of your drawing.

Experiment 2:

Make a sedimentator:

A sedimentator tube shows the different layers of soil and the way is settles in water. You can easily make one to show the make-up of your soil sample.


    • 1 cup of dry, finely crushed soil (remove grass, sticks, stones, and leaves)
    • 1-quart clear glass jar with lid
    • dishwasher detergent
    • pencil
    • water
    • ruler
    • index card or a white sheet of paper


  1. Sift your soil and get rid of rocks and lumps of organic material.
  2. Fill the quart jar 2/3 full of water and pour the cup of soil into the jar.
  3. Add 3 tablespoons of detergent, cover the jar tightly, and shake well for 5 minutes.
  4. Set your jar on a flat surface. Let it settle and measure the different layers that you see.
  5. Place the index card next to the jar and mark on the card where each layer of soil has settled.
  6. Record your measurements


How many total inches of soil are in the jar?

How many inches of sand are in the jar?

How many inches of silt are in the jar?

How many inches of clay are in the jar?

Experiment 3:

How much water can the soil hold?


    1. 2-4 cups each of several soil types (sand, loam, clay, etc.)
    2. aluminum Pans ( 2 or 3)
    3. large funnel
    4. large measuring cup
    5. scissors
    6. water
    7. 1/2 Gallon plastic milk carton (a 2 liter soda bottle works also), one for each soil sample

Before you Start:

      1. Put many very small holes at the bottom of your empty milk jug. ( A jug for each sample) Make sure you cut the top off of your jug.
      2. Get your samples of dirt.
      3. Fill your jug half way to the top with your soil. Be sure to put the same amount of the different soils in each jug. Label your soil types.


1. Hold the jug of soil over an aluminum pan and very, very slowly pour a measured amount of water on the soil allowing the soil to soak up the water.

2. Now collect the drainage of the water in the aluminum pan and slowly pour it back through the soil. Measure the amount of water that drained through. Subtract from the original amount to calculate how much water the soil absorbed. Record your results.

3. Repeat the process with several types of soils. Which soil holds the most water? The least? Why is this important to know?

Experiment 4:

Measure the anchorage strength of plant roots in different types of soil. Wind is the initial cause of uprooting and overthrowing of plants. That is why this action is also called wind throw. Since wind exerts pressure on the plants from the side, in this experiment we test the effect of a similar force for different types of soil.


    • Clay (5 lbs)
    • Silt (5 lbs)
    • Sand (5 lbs)
    • 4 identical ceramic or plastic pots
    • 4 one foot long wood dowels (3/8″ is a good diameter)
    • Spring Scale (MiniScience part# PSS_US1 or PSS_US6)


1. Make four different types of soil by mixing different proportions of clay, silt and sand. You may use the following table as a guideline for your soil types.

2. Mix the soils thoroughly.

3. Label your pots with Equal Mix, High Sand, High Silt and High clay.

4. Hold the wood dowel in the center of the pot while you add the dry soil of each type to the pot with the same label. Only 3 inches of the wood dowel must stay in the soil and the rest must stay outside. You may want to mark the 3 inch line in advance.

5. Make sure that you add equal amounts (by weight) of each type of soil to each pot.

6. Add equal amounts of water to the pots to make the soil moist. Wait 24 hours and water the pots again. Wait another 24 hours and then you will be able to start your tests.

7. Use a spring scale to pull the upper portion of the wood dowel to one side. Record how much force did you need to cause initial movement on the wood dowel? How much force did you apply to bend the wood dowel about one inch from the top? How much force did you use to uproot the wood dowel.

Soil Type Clay Silt Sand
Equal Mix 1 Lbs. 1 Lbs. 1 Lbs.
High Sand 1 Lbs. 1 Lbs. 2 Lbs.
High Silt 1 Lbs. 2 Lbs. 1 Lbs.
High Clay 2 Lbs. 1 Lbs. 1 Lbs.

Record your results in a table like this:

Soil Type Force to move Force to move 1″ Force to uproot
Equal Mix
High Sand
High Silt
High Clay

Use the results of your experiments to decide which of the three basic soil types can help support a better anchorage for the plant roots.

Experiment 5:

Measure the anchorage strength of plant roots in seedlings.


    • Clay (5 lbs)
    • Silt (5 lbs)
    • Sand (5 lbs)
    • 4 identical ceramic or plastic pots
    • 16 beans
    • Scale


1. Make four different types of soil by mixing different proportions of clay, silt and sand. You may use the following table as a guide line for your soil types.

2. Mix the soils thoroughly.

3. Label your pots with Equal Mix, High Sand, High Silt and High clay.

4. Fill each pot with the type of soil assigned to that pot. Make sure all pots have equal amounts (by weight) of soil.

5. Dig 4, one inch deep holes in each pot. Drop a bean in each hole and cover them with soil.

6. Water the pots with equal amounts of water for each pot.

7. If you want to add some liquid fertilizers to the water, follow the instruction that comes with the fertilizer.

8. Continue watering the plants daily until the seeds sprout and become a young plant. Make sure the soil stays moist, not wet. Excess water can damage the plant.

9. When young plants are ready, attach a cotton string to the stem of each plant and use the hook of a spring scale to pull out the plant from the soil. Record the amount of force required to do that for each plant. Since you have 4 seeds in each pot (for each type of soil), calculate the average force for each type of soil.

Soil Type Clay Silt Sand
Equal Mix 1 Lbs. 1 Lbs. 1 Lbs.
High Sand 1 Lbs. 1 Lbs. 2 Lbs.
High Silt 1 Lbs. 2 Lbs. 1 Lbs.
High Clay 2 Lbs. 1 Lbs. 1 Lbs.

Record your results in a table like this:

Soil Type Force to pull out out the seedlings
Equal Mix
High Sand
High Silt
High Clay

Use the result of your experiments to decide which of the three basic soil types can help support a better anchorage for the plant roots.

 What if I don’t have a spring scale?

Any soft spring or elastic rubber band can be used as a spring scale. You just need to test it in advance to see how much does it stretch for different amounts of weight. A long strip that you may cut from a balloon can also be utilized. Just remember, more flexibility will result in more stretching and more accuracy. If you use this method you will definitely need goggles to protect your eyes.

Materials and Equipment:

List of material can be extracted from the experiment section.

Results of Experiment (Observation):

Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.


You will need to calculate the average force used to pull out the seedlings in experiment 5.

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.