Digging Deeper with Soils

By Eve Pranis, June 23, 2008

Your students' inquiring minds will provide fertile ground for extending soil investigations and activities. Here are some ideas to prompt your thinking.

  • Explore how and why soils vary throughout the global garden. Have students brainstorm, then research to find out why soils differ from region to region and throughout the world. (The important factors that affect soils include "parent" rocks, climate, time, types of plants and animals present, and slope.) Ask students, teachers, and parents to bring soil samples back from travels, then examine and compare the soils and learn about the areas from which they were taken. Find e-mail or pen pals willing to swap soils, information, and experiences.
  • Write descriptive soil poems. Bring in or have students bring in soil samples to display next to large sheets of paper. Have small groups visit each sample, observe it, then have each student write down an adjective to describe it. Next, have each group use its collective descriptions to write a poem about soil. Finally, mix up the poems and invite the class to guess which sample each poem describes.
  • Examine whether plant roots seem to "prefer" particular types of soils. Challenge students to design setups to determine whether plant roots will tend to grow toward a particular soil.
  • Have students investigate modern agricultural techniques. Explore how they both enhance and diminish soil health and productivity. For instance, large equipment compacts soils, growing the same crop in the same spot every year "robs" certain nutrients, and row crops can lead to erosion. In contrast, practices like cover cropping and contour farming protect and enhance soil.
  • Investigate plants that are adapted to survive in specific soil conditions (e.g., many bog plants are carnivorous because acidic bog soils lack adequate nitrogen).
  • Expand your horizons! Have students investigate the characteristics of natural soil layers or "horizons." You can view these layers best in an exposed bank or gully where the soil is exposed to a depth of 3 or 4 feet. The soil surface may have a layer of undecomposed organic matter. The next layer, topsoil, is typically looser and darker than lower soil layers because it contains the greatest amount of humus and soil life. The subsoil, which is more compact and generally lighter colored than topsoil, may begin a few inches or several feet deep. It contains little organic matter and few living things. Below this is weathered bedrock. After comparing the characteristics of topsoil and subsoil, students may want to predict which type will promote better plant growth, then experiment to test their hypotheses.
  • Conduct a simple simulation to get kids thinking about erosion. Fill a shallow pan with soil, prop it up a couple of inches at one end to create a slope, and set up a collecting basin below the tray to collect runoff. Holding a watering can a foot above the soil, sprinkle "rain" for a minute or two. After helping students make connections between the simulation and what happens outdoors, challenge them to consider some ways farmers and gardeners might reduce erosion. Student ideas might include mulching, terracing, planting a crop of grass, or adding organic materials to improve water absorption. Have students design setups to test their ideas.

Assessing Soil Savvy

Consider some of the following activities to help you and your students assess what they've learned from their soil adventures.

  • Create a culminating celebration that enables students to showcase their experiences and understanding about soils. Brenda Mangum's third graders in Sterling, VA, held what they called "The Great Soil Conference" for an audience of parents and administrators. They displayed descriptions, data, and conclusions from their soil-based research and experiments -- drainage tests, the effects of worms in different soil types, pH testing, and so on -- then invited parents and administrators to review the displays and participate in hands-on activities.
  • Have students design "advertisements" about soil. Make sure they include information that reflects what they know about soil.
  • Be soil detectives. Give students an unfamiliar soil mixture, then challenge them to use "tests" they've learned to infer what ingredients the soil contains or to choose which they would prefer for growing plants. Have them defend their answers. Alternatively, bring in mystery soils and have students observe them and describe what they can infer about the location from which each soil was taken.

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