Background Information
Earthworms are members of the Animal Kingdom, belonging to the Phylum Annelida. They are commonly called night crawlers because of their nocturnal characteristics. Earthworms are characterized as having long tube-like bodies with many segments. There is an enlargement made up of several segments that house the clitellum, a glandular organ used for reproduction. These animals are hermaphroditic, so they can function as either male or female during reproduction.
These animals are extremely valuable resources to humans and the environment. They are a source of food, mainly protein, in many cultures. They can also be used as bait for fishing, and most importantly, they play an important role in conditioning the soil. Earthworms act as agents of soil aeration and provide nutrients to the soil.
Earthworms benefit the soil in many ways, mainly due to the physical and chemical effects of their casts and burrows. As earthworms burrow through the soil, they excrete waste made up of soil and digested plant residue. As these items pass through the digestive tract of the earthworm, their gizzard breaks them down into smaller particles. These casts modify the soil structural units that are made up of plates and blocks, into finer, spherical granules. The spherical granules of soil are further decomposed by other earthworms and microorganisms in the soil. The casts also provide nitrogen in a usable form for other organisms that decompose organic matter on the soil surface. Comparative analyses have shown soil surrounding worm casts to contain as much as five times more nitrogen, and even higher compositions of potassium, magnesium, phosphorous. The soil even contains one-and-one half times more calcium. Scientists credit the increase to the earthworms’ ability to liberate nutrients from particles of both organic and mineral matter that would otherwise remain unavailable to plants. (Delahaut & Koval)
Project Overview
In this experiment, students will be asked to raise several varieties of bean seeds in containers. Each will use the same soil mixture; only one set of plant seeds will have worms in the container. The students will make a hypothesis based on the background information above and any other research they obtain concerning how the worms will affect plant growth. The students will make weekly observations for about two months, analyze the data and formulate a conclusion. Based on how elaborate the experimental design is, the students will decide on how many worms, container and types of seeds needed.
Materials
-
A variety of bean seeds
-
40 to 60 earthworms
-
Styrofoam cups or empty milk carton
-
Containers with proper drainage to plant seeds and/or house earthworms
Dry bean seeds can be purchased in supermarket in large quantities for about one dollar. Even though worms can be found outside, it will be better to use earthworms from a bait shop. You can usually buy them by the dozen for about one dollar and fifty cents per dozen. These worms are usually thick and healthy and are raised under fairly good conditions.
Procedures
-
Place a couple of small holes in the bottom of a stryrofoam cup or milk carton.
-
Fill each of the container half full with potting soil.
-
Place one bean seed in each of the containers.
-
Cover the seeds with potting soil, but do not fill the container to the top with the soil.
-
Water the seed, and do not allow the container to become dry. Be careful not to over water the seeds.
-
Allow the plant to germinate and grow approximately one to two inches.
-
While waiting for the seeds to germinate, prepare several worm farms to place with the repotted bean plants. (See direction for making a worm farm in the “additional lessons” section at the end of the paper).
-
Repot the plants into a container that can hold up to three of the plants. You may have to remove some of the soil around the plant. Be careful not to destroy the plants roots.
-
Gently pour the worm farm into a container with the three bean plants. Place additional soil in the container if needed.