When children work with soil (or dirt as they most often call it), they rarely question where it comes from. Soil, sky, water…they just are. But when they view soil as one component of a garden, one part of the system for growing plants, they may gain enough experience with it to begin classifying it as “good,” “bad,” “hard,” “wet,” and “dry.” In some regions, children may notice the presence of sand grains and clay. Feeling soil and squeezing it into a “ribbon” in your palm is one way soil scientists notice the properties of soil. When bedrock (the rock that lies under the soil) is visible, children may more easily identify how tiny pieces of rock become soil through the process of erosion. Learning how soil is formed through erosion of rock begins in early childhood with experiences but full understanding is not expected until grade 4 or later (see NGSS performance expectation 4-ESS2 Earth’s Systems). No rush!

To easily view the materials that are in soil, put a trowel-ful of it in a clear jar, add water but leave some space at the top, and shake well before letting all the parts settle for several hours or overnight. Put a tightly fitting lid on the jar before having the children shake it! I like to use a jar that is easy for preschoolers to handle, such as a mayonnaise jar. Put tape around the lid to remind children not to open the jar and keep it available for as long as the children are interested. They will return to it over time, shaking and then viewing the results again and again. What will the results be? That depends on the composition of the soil that was put into the jar. There will be some organic matter (bits of dead leaves, roots, maybe an insect or worm), small pebbles, sand, silt (smaller than sand grains but you can still feel them) and clay (very small but you know it when you feel that slick stickiness). These materials will settle out into rough layers, especially when given a long period of settling. Teachers and upper elementary students can follow more detailed directions in the Field Museum’s Underground Adventure webpages.  Retired teacher, Moira Whitehouse shared a fifth grade level slide show on soil properties that is useful for teachers to adapt for other ages. The GLOBE Soil Module has background information in a teacher implementation guide for a series of activities. The information can be adapted for your students.

“Mud kitchens” are another way for children to explore the properties of soil as they mix soil and water to create confections and concoctions. Muddy Faces offers a download of Jan White’s ebook, Making a Mud Kitchen, with free registration. She writes, “There is little more important in our physical world than earth and water and they are truly intriguing things, especially when they interact.” Imaginative play engages children for long periods of time, allowing time to make observations and discoveries and test out ideas.

Search the archive of articles and columns in Science and Children to learn more about investigating soil. In “Teaching Through Tradebooks: The Dirt on Soil” (September 2007) columnist Christine Anne Royce suggests books, describes activities for two age ranges and offers these safety guidelines:

1. Know the source of your soil samples! Soil can be contaminated by pesticides, animal waste, etc.
2. Obtain parent/guardian permission before having students work in soil or in compost to inform them of possible allergens (mold/spores, etc), which might affect students with compromised immune systems, allergies, or asthma.
3. Have students wear plastic gloves and make sure all open cuts or scratches are covered minimally to prevent infection, and always wash hands with soap and water after working with soil or compost. Wash desktops with mild soap and water where soil activities took place. Do not allow snacks or other food products during soil activities. Don’t keep wet soil more than a day or two. Mold and bacteria spores will grow in it.
4. Wear appropriate clothing (long sleeves and pants) and closed-toed shoes or sneakers when working in a compost pile.
5. Handle compost materials, wire mesh, stakes, wooden boards with care and caution. Use only nonmercury thermometers.

And of course, always wash hands after working with soil.

Although organic matter is only a small part of soil, it provides nutrients and helps keep the soil loose with space for air. Building organic matter into garden soil is one reason to compost scraps of fruits and vegetables from the kitchen or classroom snack. In the March 2016 issue of Science and Children I wrote in the Early Years column about how children in one preschool are adding to a minimalist compost pile. Over time they have observed the decomposition of pumpkins and apple peelings into compost. Does your program compost?