Science Buddies: "Ask an Expert"

Feeding Earthworms: Do Different Diets Affect Them and the Soil They Enrich?

I am doing this project for school but I need a hypothesis. Which one seems like it would work better?

- That as the energy content of the given diet increases, the number of worms in the earthworm colony increases, as well as the height and condition of the plant grown in the worm-fertilised soil.
- That as the sugar content of the given diet increases, the number of worms in the earthworm colony increases, as well as the height and condition of the plant grown in the worm-fertilised soil.
- That as the healthiness of the given diet increases, the number of worms in the earthworm colony increases, as well as the height and condition of the plant grown in the worm-fertilised soil.

I would like an answer to this by Sunday or Monday if possible Thank you so much!

How about something a little more simple and straightforward (and easier to test):

That as the available nutrients in the soil increases, the productivity of worms in the earthworm colony increases, as well as the height and condition of the plant grown in the worm-fertilized soil.

Are you going to test this with the following controls:
plant with high nutrient soil, no worms
plant with low nutrient soil, no worms
plant with high nutrient soil, worms
plant with low nutrient soil, worms

Are you predicting that the plant in low nutrient soil with worms will do better than the one in low nutrient soil without worms? That the worms themselves will be providing nutrients to the plant as they do their worm business? Otherwise it will be hard to separate the benefit of high nutrient soil with or without worms (both plants will do well and better than the low nutrient soil plants).

Hi,

Stephgreene has provided an excellent suggestion for setting up your experiment with controlled conditions. How are you going to measure your results?

Here’s an earthworm project from the science buddies website that includes useful background information and suggestions for setting up an experiment. You could adapt this to your idea. Remember that you will want to obtain measurable results.

https://www.sciencebuddies.org/science- ... p041.shtml

Donna Hardy

Hi, thanks for your suggestions.
But the plants would obviously grow in soils with high nutrients, wouldn't they? So maybe I should just test the worms?
And do you just add nutrients to the soil through fertiliser?

Hi,

It’s good that you are thinking carefully about your experimental protocol. For a successful science fair project, you need to formulate a question that you can answer with a controlled experiment. What is your question? Plants will grow best with optimum water, light, temperature and fertilizer; a very high concentration of fertilizer could be toxic to both plants and earthworms. Are you interested in finding out the best conditions for growing plants or growing earthworms?

If you look at the experimental matrix that stephgreene suggested, there are two conditions for growing plants (high and low nutrients) and with and without worms. This would be a very nice experiment to test the effect of worms on the growth of plants under two different conditions.

What type of plant are you going to use, and what is the optimum fertilizer for this type of plant. What will you do to provide optimum conditions for the earthworms in each sample/ Try to do a little more background reading and find out what types of fertilizer are available and what earthworms like to eat.

For a science project, you will want to control all experimental conditions except your independent variables (plants and worms). Everything else (light, moisture, temperature, soil, etc, should be identical.

I hope this helps. Let us know if you have other questions.


Donna Hardy

Do you think I could do an experiment instead of varying the energy of the food, I could vary the amount of nutrients?

By the way, I told my science teacher the nutrient idea but he didn't like it as much as the energy one.
But I'm just worried, I'm varying the energy in the different diets but the amount of vitamins and stuff in them changes, so that could have an effect...

Hi,

I think the reason you are having a difficult time deciding what to do is that your project doesn’t appear to have a purpose yet. Once you can identify a purpose, you will be able to ask a question that can be answered by an experiment. What do you want to find out about earthworms? Or, what do you want to discover about growing plants? I recommend doing more background reading from scientific sources about plants and earthworms. This will give you ideas for developing your topic and help you understand the science behind your project. A good place to start would be to find out what earthworms and plants require for a habitat and nutrient sources.

The science buddies website has excellent resources for inspiration and for planning your project. Try reading through these project ideas and read some of the references to get an idea of what a scientific experiment is.

https://www.sciencebuddies.org/science- ... p041.shtml

https://www.sciencebuddies.org/science- ... p061.shtml

https://www.sciencebuddies.org/science- ... p049.shtml

https://www.sciencebuddies.org/science- ... p002.shtml

https://www.sciencebuddies.org/science- ... p046.shtml

Once you have selected a specific topic, you will be able to design a suitable experiment. Ideally, you will want to do just one experiment and change just one variable (food, temperature, water, or whatever) and keep all other conditions the same (controlled).

I hope this helps. Let us know if you have more questions.


Donna Hardy

I want to find out the best food to feed earthworms to achieve the best turnover/results. This would be useful to the community and farmers everywhere who use worm farms.

Hi,

Perfect. Great question! Now, from your background reading, what kinds of foods to earthworms like to eat? Here is some information about what earthworms like and don’t like, and what to avoid giving them.

http://www.vermicompost.net/worm-compos ... s-eat.aspx

For your project, is there a particular type of organic matter that could be potential earthworm food that you would like to test? Something that causes a problem like water hyacinths or kudzu vine? Or perhaps something that is an environmental problem in you local area? Spend some time on this part of the project, as the selection of organic matter will help make your project unique. You can have more than one test food; the food source is the independent variable for this project.

Next, you need to plan an experiment where you can grow worms and measure what the worms eat. From the earthworm project ideas on the Science Buddies website, do you have an idea of what kind of container you can use to grow earthworms? Since this is a science project, you will want to include a positive control using a food that that earthworms really like such as pumpkin, corn cobs, or melon rinds. You will also need a negative control that will contain no worms. Do you have access to soil that is optimum for earthworm growth? Do you have a place where you can keep all of the containers so they will be exposed to identical temperature, sunlight, and moisture? Do you have a way to cut up the organic matter so all samples are provided in pieces that are about the same size, e.g. 10 mm pieces? Do you have a source of healthy, growing, eating earthworms to start the experiment (don’t use worms from the bait shop)? Do you have enough containers to set up the experiment in duplicate?

How are you going to measure your results? You should plan to weigh the food source that you add to each container so you will know what is consumed. You can also weigh or count the earthworms at the beginning and at the end of the experiment. Can you think of anything else to measure? I recommend recording temperature and soil moisture to make sure it is consistent with all of your samples. It would also be a good idea to take photographs of your project as you go along as these will be helpful when you write up your board.

I hope all of my questions will help you plan a good experiment. Paying meticulous attention to the details and selecting a unique food source will make this an outstanding project.

If you will let me know the details of your plans, I’ll try to make additional suggestions.

Donna Hardy

I emailed my science teacher and he said maybe try different diets eg one high in protein, one in carbohydrates and lipids and testing the effects from that. Here's my method if you want to get a better idea


METHOD AND EQUIPMENT - Outline how you will conduct a valid scientific investigation. List equipment you will use.

200 ‘red wriggler’ earthworms
10 20x20cm pots with drainage holes at bottom
10 drainage trays to be placed under the pots
Garbage bags to cover pots
Unfertilised potting soil
Shovel/scoop for soil transfer
Water and spray bottle
Ruler
Metric scale
Gardening gloves (optional) for handling worms and soil
4 different types of food, ie vegetables, fruit, eggshells, coffee grounds, leaves and grass
Camera and/or notebook for recording results
30 mung bean seeds
30 sunflower seeds
Skewer

STAGE 1
1. Place unfertilised potting soil into each pot so it reaches to about three quarters of the way up. To ensure that the soil is damp, pour 100mL of tap water in each pot. The soil should form a ball when squeezed in the hand. Pat down the soil so it is more compressed, and, if necessary, add more soil so the level remains at three quarters. If any water has drained out, empty out the drainage tray.
2. Using the electronic metric scale, weigh the empty cup and ‘zero’ the scales.
3. Select 20 worms to put in the first pot, preferably of a similar size and length. Weigh the container now with the worms inside and record this number. This is the starting group weight of the colony. If possible, take a photo or measure the length of a worm so you can compare it with the end results later.
4. Gently pour the worms out of the cup into a pot and cover with additional moist soil. The soil should be no less than 10cm from the top of the pot.
5. Cover the pot with a dark-coloured plastic bag and poke some air holes in it with the skewer.
6. Repeat steps 2-5 until all pots are inhabited.
7. Place pots side by side in a dark, cool area. Make sure each has a drainage tray.
8. Prepare the food. Each pair of pots will have a different type of food for the next month. Make sure that the worms are fed around the same amount of food and water every 2-3 days so the energy content does not differ too much. Label each pair of pots with the food they will be given. As a control, do not feed the 5th pair of pots, but only provide water at the same times as the other pots.
9. Record, for each pot, what is done and observed every 2-3 days, including any observations of the soil quality, worm activity, how much of the food has been eaten, amount of worm castings and any drainage coming out of the pot.
10. After a month (longer if possible), empty out each pot one at a time and count all the worms, noting any size or appearance changes. Separate the worms from the soil and weigh them in the same way as step 3. Record their weight, number of worms and note any appearance changes.
11. Put the soil and worm castings back inside their original pots. Put the worms in the garden.

STAGE 2
12. In each pot, plant 3 sunflower seeds and 3 mung bean seeds all at the same depth. Water all pots and put side by side in light conditions.
13. Check back each day and note any observations in the growth rate and appearance of the plants as well as measuring and recording their height. Water if necessary.
14. Record results in table and then graph them.

Thanks so much for the help!

Hi,

Thanks for posting the details of your experiment. This is a very complex project. Here are some comments that might be helpful:

1. Try counting and weighing the worms before and after the experiment. This is a little difficult as healthy worms do not like to sit still outside of soil to be counted or weighed, but do the best that you can. The problem with your protocol is that you are weighing the pot with the soil and there will be a variable amount of moisture in the soil that will make your results invalid. This measurement is important because presumably the increase in earthworm mass will correspond to the amount of food they are able to utilize.

2. The information available on foods suitable earthworm foods suggests not feeding high protein or high lipid foods to earthworms. The problem is that these foods attract other pests like rodents and flies, which you don’t want to do. In a science fair project, you want to improve on what others have learned in the past, you don’t want to reinvent what is known not to work. So please do more background research on the foods that are suitable for earthworms. You can add originality to your project by your selection of foods. Please note that eggshells are composed of calcium carbonate, and adding eggshells to all of pots would be beneficial to the earthworms, but they primarily need organic matter to consume for energy and growth.

Here are some sites that give specific information what to feed earthworms and what to avoid:

http://www.nyworms.com/ecare.htm

http://www.howtocompost.org/info/info_wormfaq.asp

http://www.vermicompost.net/worm-compos ... s-eat.aspx

4. Your protocol includes a feeding every 2-3 days. The worm websites all suggest adding more food as soon as the last food disappears. This avoids adding too much food that can spoil; also healthy earthworms can consume a lot of food, so you might need to add more food every day once the worms are established. I recommend checking the pots every day and add more food as it is needed. You should record the amount of food you add to each pot.

5. Your experimental protocol appears to include one pair of pots with earthworms that are not fed at all. Are you planning to starve these earthworms? For your negative control, I would recommend just using a pot of soil with no earthworms and no food added. You can compare results of the plant growth using soil that has not had any earthworms living in it.


4. This is really two projects; growing earthworms and then growing plants. You should not use two different types of plant seeds. Grow 6 sunflower or 6 mung bean seeds in each pot and measure each plant for a more statistically significant result.

5. In your experimental protocol, you need to state how you are keeping all parameters other than the independent variable (earthworm food in each pot) controlled. You should measure soil moisture, temperature, and size of food particles.


I hope this helps. Good luck.

Donna Hardy

1. That's what I'm doing? I'm not weighing the pot with the soil, I think you misread the instructions.
2. In fact, the first site you sent me recommended a high-protein mash. I think I'll feed one pot high calcium, so just eggshells.
4. Ok!
5. I got that idea from your experiment. Look!
Place a layer of one type of food into each of the four pots. As a control, a fifth pot should receive water only, no additional food source.

4. Ok.
5. I state that later in the experiment action plan.