Some objects decay much faster than others.
The difference in decay rates can be demonstrated using the following steps. Place 10 cm to 20 cm of soil in each of the three large glass containers. Obtain a biodegradable product, such as a piece of paper, a nonbiodegradable plastic lid, and several plant leaves. A biodegradable substance is one that can be broken down by natural environmental processes. Bury each item about 5 cm deep in a separate container.