How Do Worm Diets Effect The Soil?

Georgina Bourbon

Background Info

Soils are composed of five main components:

  • mineral particles derived from rocks by weathering;

  • organic materials - humus from dead and decaying plant material;

  • soil water - in which nutrient elements are dissolved;

  • soil air - both carbon dioxide and oxygen;

  • living organisms including bacteria that help plant decomposition.

Worms cause nutrients to circulate the soil by transferring what they eat into waste, they cause the soil to loosen and allow for more nutrients to enter in other ways. This is important because it allows for plants to thrive.

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The purpose of this experiment is to see how earthworm diets affect the soil they enrich. Earthworms have always been known as great garden friends but how to make these friends the most productive is the question. Over the course of a 1 1/2 months 2 different diets being will be tested on 2 different colonies of earthworms. The diets include a vegetable diet, fruit diet, and a grass and leaves diet. Soil analysis will be measured at the end of each week to track the difference. The results of this experiment will help all gardeners be more productive.


If the earthworms are fed different diets then the nutrients they consume will be put into the soil.

Parts Of Experiment

Dependent Variable-Ph, Phosphorus, Nitrogen, and Potassium

2. Independent Variable – Soil Nutrient level

3. Control – Pot of Plain soil no worms

4. Experimental Group-Red Worms

5. Factors Held Constant; Pot and Type of worm



  • 50 Earthworms

  • Soil test kit that tests pH, Nitrogen, Phosphorus, and Potassium.

  • 2 ten-inch diameter plastic pot with drainage holes on the bottom

  • Black plastic bags with small holes or blankets with small holes to cover the pots.

  • Catch trays if needed to place under the pots for drippings and escaping worms

  • Spray bottle to keep worms moist

  • Newspaper

  • Gardening gloves, if you prefer, for handling soil and/or worms

  • Notebook

  • Pen or pencil

  • 1 Large bag of soil

Earthworm Diets

  • 2 buckets full of leaves and grass

  • Assorted vegetables 2 lbs at least(Zucchini, squash, sweet potato, Cauliflower, Carrot, Broccoli)

  • Assorted Fruits 3 lbs at least(Nectarine, peach, banana, apple, pineapple, cantaloupe)

  • knife

  • 3 plastic bowls with 8 inch diameter

  • Cling wrap


The Earthworm Set Up

  1. Fill the pots about 3/4ths of the way up with potting soil. Add some water and compact the soil, repeat till 3/4 of pot is full for each pot.

  2. Let the pot/soil drain for at the very least 30 min, so as not to drown the worms.

  3. Place 15 earthworms in each pot if there are extra worms just put them in your outside soil.

  4. Place moist soil on top of the worms, adding until you reach about 2 inches from the top of the pot.

  5. Wrap a black blanket or black trash bag around the worms to keep their habitat dark and warm.

  6. Make sure to keep the worms in a cool place and have a drainage pot under for any drippings.

Earthworm diets

  1. Choose which diet to start with and take your fruit, vegetables, or leaves and grass and cut into small pieces.

  2. Keep the fruit and vegetables refrigerated as cut pieces in a bowl covered with cling wrap

  3. Feed earthworms twice a day, once in the morning and once in the evening. Feed about a 1/2 cup to begin with but as the 2nd week comes round move up to a 3/4. This will require more food.

Start Your Experiment

  1. Prepare a data table for each pot to record what you do and observe. Include: start date, date and time of food additions, nutrients in food and amount, date and amount of water added, along with any other special notes about the food's appearance, worm activity, or pot drainage.

  2. Place a layer of one type of food into each of the four pots.

  3. Follow the instructions that came with a soil analysis kit to measure the acidity (pH), and relative levels of potassium (K), nitrogen (N), and phosphorus (P) of the soil from the control pot or from the potting soil bag.

  4. Sprinkle some water on top, if needed, to keep the food and soil moist.

  5. Cover the pots with black plastic bags; be sure the air holes are still at the top of the pot.

  6. Label each pot with the type of food it received.

  7. Check the pots every 2-3 days, and add food every other day and water every day..

  8. Record the food and water additions each time you make them. Also make notes of what you observe in each pot.

  9. Follow the instructions that came with a soil analysis kit to measure the acidity (pH), and relative levels of potassium (K), nitrogen (N), and phosphorus (P) of the soil from each pot and compare.

  10. Record the soil analysis results for each pot in your notebook.


10-20-14: First day, took soil test and made habitats for worms and added worms. I am worried that the pots may be too small.

10-21-14: the worms are settled in, but it is starting to get really cold.

10-22-14: the worms seem to really like acidic food, the grapefruit i fed them disappeared faster than the apple.

10-23-14: Same old same old, no real change. The test shows a slow but steady increase.

10-24-14:The pH level stays the same unless the worms consume something acidic, it doesn't stay it the soil long though, I wonder why?

10-25-14 There was a flash freeze last night and the worms and the soil all froze, the worms have died, I'm going to have to get a new batch and start over.

10-26-14:Getting the new worms today, I researched how to keep worms warm in winter, the site said that worms like the cold but that blankets would be necessary if temperatures were really bad.

10-27-14: The new worms, are fatter/bigger than the original ones. Everything is normal besides that.

10-28-14: I like taking care of these worms, its kinda fun. They continue to eat all the food I give them, they like parsnips and grapefruit A LOT!

10-29-14: Getting up early is very tiring, these worms better give me good results. The soil needs to be watered so that it is not dry.

10-30-14: I have been feeding them a diverse diet and I'm not sure how this will affect my data I think it may cause problems, the data is increasing in certain levels then fluctuating.

10-31-14 Halloween!! The worms have multiplied there seems to be about 35 worms in the vegetable bucket.

11-1-14 November is here, the weather is supposed to get colder so I bought two blankets to wrap around the pots to keep the worms fairly warm

11-2-14: Data for pH is increasing nitrogen is decreasing and others are fluctuating. worms are fine, I fed them orange and Zucchini

11-21-14: There are getting to be to many worms so I bought a bigger pot and transferred them

11-29-14: There is a visual difference in the soil one is darker the other lighter

12-19-14: Almost done.

12-20-14: Finally got all the results I needed and have begun the calculations, the worms are now living in my wonderful garden and are helping me start a compost pile.

Statistical Analysis

The statistical analysis shows no correlation over all. It also shows a randomness to the data, it fluctuated based on what was fed, and the nutrients in the food given. It is seen from standard deviation that the nitrogen level stayed the same at 25 and that the Potassium had a high fluctuation at 12.1304, this leads to the conclusion that human errors took place.


There was no clear trend, it was very scattered with fluctuations the nitrogen had a standard deviation of 0 while the potassium had a standard deviation of 12.1304, this shows an error occurred, a human error. The averages for the levels of the soil however were quite low for healthy growing soil, Potassium had an average of 249.42 which for healthy potting soil a recommended potassium level between 200 and 360. The claim that worm diets affect the nutrients in soil was proved to be correct. The data showed a change in the soil, if the soil was not affected then no change would occur. But due to there not being a positive correlation it shows that the hypothesis was wrong. This may have been because of an error in the experiment planning leading to incorrect data. To have a clear result, one that could be trusted many changed must be made to allow for a more successful experiment.


The hypothesis that if the earthworms are fed different diets then the nutrients they consume will be put into the soil was proved incorrect but the hypothesis is very broad in conclusion the nutrients fluctuated in the experiment. The purpose to learn and create a diet that was beneficial to both worms and soil was achieved.

Sources Of Errors

Errors and inaccuracies in the design and execution of this experiment can be categorized in three ways. Human errors in the carrying out of this experiment comprise of the first category. Some errors in this category include that the environments were not exactly alike, one pot may have had more soil or was slightly more moist than the other, these small mistakes are expected in any experiment and were undoubtedly present in this lab. another group of errors might have been the amount of food given for each, a cup was measured out, but the food was cut up in different shapes and sizes so one pot may have gotten more food than the other. All of the errors listed above may have caused inaccurate data.

Environmental sources of error make up the second category. These types of errors were unforeseen by the executor of the experiment and not written into the experimental design. When the experiment was first started there was an unexpected flash freeze causing the worms used to die. A second batch of worms was purchased to continue the experiment, but the results were most likely skewed because a different control group was added..

The third and most important category of sources of error came from flaws in the design of this experiment. The experiment would be best conducted in the early fall when it is not to cold or hot to allow the worms to function as normally as possible. There should have been a marked place for the soil testing to use, and a longer incubation period to allow more data therefore greater accuracy.


This experiment directly relates to gardeners and any environmentalists who want to have a compost pile or a garden. Worms are some of the best "fertilizers" in this world and can add many nutrients into soil enriching it for plants who grow there. The results of this experiment will help garden enthusiasts have a more successful garden and also may help prevent their trashcan from smelling so much by giving the worms their leftovers. This is important to more than just the obvious people but to everyone on this earth, because we want to live on a healthy and happy world and this is one way to take care of our planet.


As stated in the sources of error and inaccuracies a few things could have been done to help this experiment. The food needed to be cut in a more standard shape and size so that the pots got "equal" amounts of food. The same is said for the set up having more equal soil portions and such. There should have been a specific place that the soil test should occur . A continuation of this experiment would be very helpful, because a longer period of experimentation helps the results be more accurate. The continuation could test how the worms affect plant growth.



"Common Earthworms, Common Earthworm Pictures, Common Earthworm Facts - National Geographic." National Geographic. The National Geographic, n.d. Web. 29 Sept. 2014.

Science Buddies Staff. "Feeding Earthworms: Do Different Diets Affect Them and the Soil They Enrich?" Science Buddies. Science Buddies, 6 Oct. 2014. Web. 8 Oct. 2014

"The Dirt on Soil - Learning Adventures." The Dirt on Soil - Learning Adventures. Discovery Channel, n.d. Web. 29 Sept. 2014.

"Why Is It Important to Eat Fruit?" Health and Nutrition Benefits of Fruit. US Government, n.d. Web. 27 Sept. 2014.

"Soil Fertility." Soil Fertility., n.d. Web. 29 Sept. 2014.

"SOIL TESTING." Soil Testing. US Government, n.d. Web. 29 Sept. 2014.

"Arithmetic Mean (Average) - GMAT Math Study Guide." Arithmetic Mean (Average) - GMAT Math Study Guide. Platinum GMTA, n.d. Web. 05 Jan. 2015.


Howard, Doreen G. "Building Fertile Soil." Mother Earth News. Mother Earth News, June-July 2013. Web. 29 Sept. 2014.