3. Soil Analysis - Lesson Plan

Lesson Plan

  1. Discuss the Comparing Soil Homework from the night before. This assignment asks students to observe and compare 2 samples of soil, one from home, one from school, and to devise original tests to look for differences between the soils. Some examples of questions to ask:
    • What did you observe about the school soil? about your home soil?
    • What was similar? What was different?
    • What ingredients make up soil?
    • What test did you try?
    • What did you discover?
    • What other tests could we use?
  2. Show and pass around the ziplock bags of clay, silt and sand. Allow students to make comparisons between the different materials and lead them to the conclusion that clay, silt and sand are all made of rock that has been ground down to different sizes, clay being the smallest, sand being the largest. Begin a list of soil "ingredients" on the board.
  3. Pass around the ziplock bag of compost. Discuss what compost is (dead, decaying organic material) and where it comes from. Discuss whether compost is good or bad for soil and consider the reasons why.
  4. Ask the students what other ingredients are in soil and complete the list on the board. The major other components include water, air, living things, and minerals.
  5. Optional: Discuss whether all soils have all ingredients and what the effect of missing ingredients might be.
  6. Introduce today's lab and offer a brief explanation of the 4 stations students will rotate through. Ask the question why are we comparing soils and what would we want to discover?
  7. Specify the organization of the student's lab notebook and decide how data should be recorded at each station.
  8. Divide the students into groups and specify the rotation strategy. Rotate through the 4 stations, giving students 5-10 minutes per station. Allow time for a thorough clean up at the end of each station.
  9. 2-4 days later, give students 5-10 minutes to check back on their soil separation and Tullgren Funnel tests and record their results.
  10. Engage the students in a discussion of the differences between the 2 soils. One way to do this would be to create a table at the front of the classroom with columns for each of the 2 soils and rows for each of the 4 tests. Students can offer observations and comparisons for each test to add to the summarized results at the front of the room. Some examples of questions to ask:
    • Were you surprised by any of the results?
    • What do differences in pH mean?
    • What might cause pH differences?
    • How should we interpret differences in the relative amounts of clay, silt and sand?
    • Was any layer missing?
    • How would differences in soil composition affect the types of plants or animals that could live in that soil?
    • Does knowing where the 2 soils came from help explain any of the results?
    • Did everyone get the same results? Why or why not?
  11. Armed with a thorough analysis of these 2 soils, begin a discussion of what makes soil "healthy". Challenge students to decide which of the 2 soils is "healthiest". This question is very open-ended and does not have a right or wrong answer but is an excellent way to generate discussion and delve deeply into the issue of soil quality. One way to conduct this discussion is to allow students time to speak with their group about the question first, then share the group's conclusion with the rest of the class. A key factor to bring up is whether "healthy" soil is the same regardless of its location or use (such as a garden, schoolyard, desert, forest or creek).