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The importance of earthworms to soil and plants


Introduction: (Initial Observation)

After a heavy rain, I walked outside and saw some pinkish soft worms. I was wondering where did they come from. Later when my parents were digging the back yard to plant a small tree, I noticed that these worms are under ground. Immediately I thought since worms live underground, they possibly eat plant root and maybe that is what makes some plants die. So I started to remove the worms and throw them in the garbage can.

Recently in a television program I saw someone who produces worm as her business. She was actually selling the worms to gardeners because worms are good for soil and plants.

I was totally confused by now, so I decided to select this science project and find out how can the worms be good for the soil and how can someone make money from selling earth worms. I also want to know how can we identify the sex of the worm and how can we identify adults from children? Finally I plan to learn about the life-span and reproduction rate of earthworms.


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 earthworms, their life cycle and biology. Read books, magazines or ask professionals who might know in order to learn about the effect of earthworms on soil and plants. Keep track of where you got your information from.

If you search the Internet, use keywords such as earthworm biology, earthworm life cycle, earthworm food, earthworm price and earthworm growth. Following are some information that you may find online.

When you select the earthworm project, you can go to the heart (and circulation) of the common earthworm, and explores this creature’s critical role in the cycle of decomposition and soil renewal. Without dissection or harm of any kind to the animal, you study the movement of blood through observable vessels, assess its pulse rate in response to modest temperature changes and graph the results, and in learn of its marvelous adaptability to environmental conditions.

In discussing why earthworms respond as they do, you learn about cold-blooded (poikilothermic) animals, the concept of adaptation, and circulatory systems.

Earthworm Biology and Production

Many people are interested in raising earthworms as a hobby, for their own use, or as a source of income. Much interest in vermiculture (worm-raising) has been kindled by claims that earthworms:

  1. Are a major factor in soil improvement.
  2. Increase crop yields.
  3. Can be raised with relatively little time, effort, and expense.
  4. Are easily sold at high profits for a variety of uses.
  5. Produce manure (castings) that can also be sold at a profit to florists, nurserymen, and home and organic gardeners.

In response to such claims, many people have entered the earthworm business in the last few years.

Despite extravagant claims of enormous potential markets for earthworms in agriculture, in large-scale waste disposal systems, and as a source of food for animals and even people, the major use of earthworms today is as bait for freshwater sport fishing. Some worms are also sold to home and organic gardening enthusiasts for soil improvement and composting of organic refuse. (Read more…)

Another report about growing earthworms for sale as bait for sport fishermen is available here.

THE animal kingdom of the planet earth is divided into two subkingdoms, invertebrate and vertebrate animals. That is to say, animals with backbones and animals without backbones. The invertebrate group is distinguished by nine phyla or divisions. In this group there are over 500,000 known kinds of animals, ranging from the lowest form of animal life, the protozoa, or minute, single-celled creatures, to arthropoda, which includes crabs, insects and spiders. In the vertebrate group there are well over 30,000 known kinds, including fishes, amphibians, reptiles, birds and mammals.

When it is stated that in this vast array of creatures the lowly, segmented earthworm is probably the most important to mankind, the uninitiated might aptly declare that such a statement sounds neither logical nor reasonable. Yet few creatures equal the burrowing earthworm as an essential to better health and greater growth to plant and vegetable life, and, therefore, indirectly is of the utmost importance to man.

The burrowing earthworm is Nature’s own plough, her chemist, her cultivator, her fertilizer, her distributor of plant food. In every way, the earthworm surpasses anything man has yet invented to plough, to cultivate or to fertilize the soil.

While it is unquestionably true that plants and vegetables grow and reproduce their kind without the aid of the earthworm, most naturalists claim that all fertile areas have, at one time or another, passed through the bodies of earthworms.

It is likewise unquestionably true that the finest plants and vegetables will become healthier and more productive through the activities of this lowly animal, which the ordinary person considers useful only to break the early bird’s fast or to impale on a fish hook. (Read more..)

Earthworms (also called nightcrawlers) are very important animals that aerate the soil with their burrowing action and enrich the soil with their waste products (called castings). Good soil can have as many as as 1,000,000 (a million) worms per acre.

There are over 3,000 species of earthworms around the world. These invertebrates (animals without a backbone) range in color from brown to to red, and most have a soft body. Earthworms range in size from a few inches long to over 22 feet long. The largest earthworms live in South Africa and Australia.

Anatomy and Diet: The brain, hearts, and breathing organs are located in the first few segments of the worm. It has five pairs of hearts! The rest of the inside of an earthworm is filled with the intestines, which digest its food. Earthworms eat soil and the organic material in it – like insect parts and bacteria.

Reproduction: Although each earthworm is hermaphroditic (having both male and female reproductive systems), it takes two worms to mate and reproduce. The reproductive organs are in the clitellum (the enlarged segments in the middle of an earthworm). The clitellum later forms a cocoon which protects the developing eggs.

So, what´s so great about worms? Worms are great friends to our environment. Earthworms, as they burrow and feed, swallow the soil, digest it, extract its food value and expel the residue as worm castings which are far richer in nitrogen, phosphate, calcium, and magnesium than the finest of ordinary good top soil. Worms actually MAKE rich dirt. Not only do worms create this wonderful soil for our gardens and yards, but composting also greatly reduces the amount of the garbage that is sent to our dumps and landfills.

Worms love to eat all kinds of food. They love food scraps, (but not meat, bones, or dairy products because these may cause unpleasant odors or invite unwanted ‘guests’ into your worm bin). They also eat cardboard, and even material from vacuum cleaner bags. Then they turn it into nutrient-rich compost (castings). These castings can be used as a fertilizer for all types of plants. Worm castings are the richest form of natural fertilizer known to man. This will promote higher than average growth in plants.

Earthworm Life Cycle:
Earthworms are amazingly prolific breeders. A thousand mature breeders, properly cared for and allowed to multiply, may give you half a million or more breeders, growing earthworms, and egg capsules within a year. Earthworms are bisexual, having both male and female reproductive organs. Each worm produces egg capsules, but must first be fertilized by contact with another worm. Each healthy worm, under favorable conditions, will produce an egg capsule every 7 to 10 days. These incubate in 14 to 21 days, each hatching 2 to 20 young worms, with an estimated average of 4. The new worms thus hatched will reach breeding age in 60 to 90 days, as indicated by the formation of clitellum…a thick ring about 1/3 the length of the worm from its head. The domesticated earthworm will continue to grow, after reaching the breeding stage, for perhaps six months or more before reaching its full size.

Earthworms for Soil Improvement:
The earthworm has been aptly called, “The Gardener’s Unpaid Handyman.” It tills the soil around root areas by its tireless burrowing. The burrows form channels through which root growth may reach down into the subsoil for minerals and moisture. They also absorb rainfall quickly for storage in the soil instead of allowing it to run off, carrying away valuable top soil. Most important of all, the earthworm eats, digests, and enriches dead and decaying vegetable wastes in the soil, ejecting it in the form of casts, rich in plant food value, water soluble, immediately available to plant roots. www.Workingworms.com

Earthworm Questions and Answers

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 learn about earthworms, and their effects on soil and plants. By learning about earthworms, we can benefit from their good effects and prevent any possible harmful effect.

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.

Since we intend to identify the effect of earthworms on the growth of a plant, we need to control all other variables that may affect the rate of growth. We call these controlled variables or constants. The constants in this study are:

  • amount of soil in each pot
  • size of the earthworms
  • how many seeds are planted in each pot
  • the type of pot
  • size of the pot
  • how much water is used in each pot every time
  • the amount of light
  • the depth the seeds are planted
  • the amount of compost
  • number of worms
  • soil compactness

The earthworm (presence, absence) is our independent variable also known as manipulated variable.

The rate of plant growth is dependent variable also known as responding variable.


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.

Based on my gathered information I think presence of earthworms will promote plant health and growth.

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.”



The purpose of this experiment is to determine the effect of earthworms in the soil on bean growth. We grow tow plant or two groups of plants under identical environmental conditions, however we will introduce earthworms only to the soil of one of the plants.

In this experiment You are suggested to grow beans, however my later study showed that beans are capable of building their own nutrients by getting Nitrogen gas from the air. Since we are hoping that earthworms may make the soil fertile by their castings, it is better to grow another type of fast-growing seed such as corn. It is best if you consult a local nursery and select a seed that grows best in your area.


  1. 18 Whole lima beans
  2. 5,400 mL Tap water
  3. 6 Plant pots
  4. 1,320 g Potting soil
  5. 12 Earthworms
  6. 1 Bucket that can hold 1,000 mL
  7. 1 Measuring cup



1. Place 220 g of potting soil in each of the six pots.

2. Label the first three pots with worms and place 4 earthworms in each pot.

3. Label the other three pots without worm.

4. Then poke three two centimeter, in length, width , and depth, holes in a triangle , in the middle of the container , with either your finger or pencil in all six pots.

5. Drop one lima bean in the holes in the pots.

6. Cover the seeds with the soil dug out from the holes.

7. Pat the soil down with your hand three times.

8. Get a bucket that holds 1,000 mL. Pour about1,000 mL into the bucket.

10. Water each pot with 50 mL of water using your measuring cup.

After seeds are planted:

11. Water the plants with 50 mL of water every day.

12. Make notes of how much the controlled plants grew, and how much the plants with the earthworms grew everyday, right after you watered the plants.

13. After at least three sprouts are up, start rotating the pots one quarter turn.

Your daily record of plant height may look like:

Date  Pot 1  Pot 2  Pot 3  Pot 4  Pot 5  Pot 6

In most cases you will not use the daily plant growth data and you only use the plant height measured in your final observation. The daily data may only be used to detect irregularity and eliminate some samples. For example if one of the plants dye due to some disease you may eliminate such plant from your final results.

Calculate the final average plant height in each group and report it in a table like this:

Plants with worms Plants without worms
Average plant height

Make a bar graph:

Use a bar graph to visually presentation of your results. Make one vertical bar for each group. The height of the bar represents the average height of plants (or plant growth) in that group.

Other Possible Experiments:

There are so many other experiments that you can do to learn more about the earthworms. Each experiment will provide us with answer to some of our questions.

Following link takes you to another experiments with earthworms:

How does the earthworm respond to light and gravity?

Since earthworms are important to the soil, we want to protect them and avoid using chemicals that may harm earthworms. For this reason some students study the effects of acids (such as vinegar) on earthworms. Others may study the effects of pesticides on earthworms. In all these cases you add small amounts of the chemicals to the soil and see if the earthworms can survive.

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.

What was your observation during this experiment? Which plant grow taller?

You may also include a chart to show the plant growth with worm and without worm. Following is a sample.


No calculation is required for this project.

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.