The Great Worm Hunt

Welcome to Educational Checkpoint Three – The Great Worm Hunt!

This is the third of three educational checkpoints you will have access to throughout the challenge. Each checkpoint encourages you to explore your soil health a little further, and understand what is happening underground as your undies (hopefully!) decompose.

Ever wondered how many earthworms are in your garden?

It’s often hard to work with earthworms and soil, as it’s not the easiest of things to see through. One way to find out how many earthworms are in soil would be to dig a hole and count the earthworms in the soil you remove. Two issues with this. One, dad may not like holes all over his lawn and, two, the vibrations of digging can make earthworms burrow deeper or move off.

An easier way is to get the earthworms to move to you.

To do this you will need a watering can, dishwashing liquid, mustard powder (although you may come up with alternatives, like curry powder or chilli flakes to see how they go) and a quadrat. The quadrat could be an old wire coat hanger bent into a square or a piece of string/rope 2 m long that you use to make a square pattern on the ground. (If you like math and algebra then it might be fun to think about the length of the rope and what happens to the area it encloses depending on whether you use it as a square or a circle?)

Ideally you want a bit of moisture in the soil, so this is best done after we have had some rain, because when it is dry most native Australian earthworms tend to burrow deeper into the soil.

Next, establish your hypothesis. This is what you think the outcome of your experiment will be? Ask yourself, what will happen when you pour the different liquids onto the soil? Will you recover earthworms and will the numbers differ between the treatments? If so, which solution will give you the most or the least?

Now, put down your quadrat, fill your watering can with one of your solutions (water, water and dishwashing liquid [add about 30 ml dishwashing liquid after the water to avoid too many bubbles. Can guess at this or use a medicine cup to measure out] or water and mustard powder [about two table spoons added prior to the water is enough]). Now lay down your quadrat and pour the entire watering can over the area the quadrat encloses. Over the next 5 to 15 minutes look at the soil surface and recover the earthworms that come up. Count them and perhaps give them a rinse in water before returning them to another part of the garden. Do this for each of your test solutions. What did you find? Was your hypothesis correct or did something else happen?

How does it work?

Earthworms often come to the surface when the soil becomes flooded as they require air to breath, just like us. Pouring 6-8 litres of water into a small area of soil, such as marked out by a 0.3×0.3 m quadrat fills the soil pore spaces and the worms’ burrows, which both allow air in and out of the soil. Having no air to breath the earthworms surface. This can be quite slow though as earthworms are not renowned for their sprinting prowess, so we can try and speed it up? You might consider using hot and cold water in one experiment?

What does an earthworm feel like when it is on your hand? ‘Slimy’ is a good word for it, but why is that?

Earthworms don’t have lungs like us, but they need oxygen to breath and they get this by transferring it through their skin. Their skin if you like is similar to the inside of our lungs – wet and covered in mucus. Washing up liquid is a detergent and it breaks down the worm’s mucus, so they surface to get better access to air. Mustard powder irritates and burns the worm’s sensitive skin and so they surface to get away. This is also why we quickly wash them before returning them to the soil surface.

Download - Teacher/Parent Information Sheet
Download - Student Activity Sheet