Compost Investigation

What is compost and why is it important to plants? Plan and carry out an investigation of biodegradable and nonbiodegradable matter in compost. Make inferences about why compost is important for plant growth.

Materials

• Compost sample

• Small shovel (optional)

• Magnifying glass (optional)

• Paper and a writing utensil (optional)

• Pie tin (optional)

Observation Ideas

• Use a small shovel or your hands to take a small amount of compost and spread it out on a tarp or place it in a pie tin to examine closely. Sift through the compost using your hands or shovel. What do you see?

• Use a magnifying glass to look closely at the compost. What do you notice? What materials are in the process of decomposing? The biodegradable elements that make up this compost feed the billions of soil organisms that exist in healthy soil. Does anything look like it might be nonbiodegradable? What makes you think that?

Discussion Ideas

• What do you know about composting? Have you ever composted before? Why do you think people might compost?

• What might you find when you look closely at a sample of compost? What makes you think that?

• Completely decayed organic matter, called humus, contains many important nutrients because it was previously living tissue. Differentiate between humus and organic matter that is still breaking down. What is the difference in texture, color, moisture, and density? Where are most insects found?

• Just like people digest food to break it down, the animals, fungi, and bacteria in soil are also “digesting” biodegradable materials and breaking them down. What should break down fastest: green waste (like grass clippings), uncooked vegetable scraps, cardboard, or eggshells? Why do you think that? How could you find out?

Further Investigation Idea

• How is soil different from compost? What predictions do you have and how might you find out if your predictions are correct? Look closely at a sample of compost and write down what you see, then repeat this step with soil and compare your descriptions of the two samples. Share what you did and what you found out.