Logistical tips — Erosion Table
Table size: The table in the photo was made from a discarded bunk bed, but the model can be built on any scale and with any materials, as long as it’s set up to create a gentle slope.
Soil type: A mixture of potting soil and native topsoil works well, since the potting soil holds on to some moisture, while the topsoil keeps the mix from clumping up badly. Unless the climate is particularly rainy, the table must be watered periodically so that the soil doesn’t become desiccated, which causes water to simply run off the top.
Mulch: Use straw or hay, and pull out any weeds as they appear. Shredded leaves offer the same effect.
Cover crop: Typical cover crops include peas, buckwheat, tilling radish, oats, vetch, and clover, but any plant will demon- strate the effect of roots’ helping to hold onto the soil. Don’t forget to keep this section of the bed watered regularly! Amount of water to use: This will depend on the size of the model. The demonstration in the photo required about a half-gallon of water for each of the three compartments.
Resetting the model: The bare soil will erode significantly during the demonstration, so a small hand rake is useful for evenly redistributing the soil around the box.
APPENDIX A: NGSS connections: Erosion Table activity
This activity was designed to support a number of fourth- and fifth-grade NGSS Disciplinary Core Ideas (DCIs). As a standalone activity, the erosion table demonstration directly addresses the following:
• 4-LS1-1: Plants and animals have both internal and external structures that serve various functions in growth, survival, behavior, and reproduction;
• 4-ESS2-1: Rainfall helps to shape the land and affects the types of living things found in a region. Water, ice, wind, living organisms, and gravity break rocks, soils, and sediments into smaller particles and move them around;
• 4-ESS2-1: Living things affect the physical characteristics of their regions;
• 4-ESS3-2: A variety of hazards result from natural processes. Humans cannot eliminate the hazards but can take steps to reduce their impacts; and
• 3-5-ETS1-3: Different solutions need to be tested in order to determine which of them best solves the problem, given the criteria and the constraints.
In the context of the Soil Stewardship class — incorporated with discussion and exploration of biodiversity, food webs, and human impact in a farm setting — the Erosion Table also supports the following:
• 5-LS2-1: Decomposition eventually restores (recycles) some materials back to the soil… A healthy ecosystem is one in which multiple species of different types are each able to meet their needs in a relatively stable web of life;
• 5-LS2-1: Matter cycles between the air and soil and among plants, animals, and microbes as these organisms live and die; and
• 5-ESS3-1: Human activities in agriculture, industry, and everyday life have had major effects on the land, vegetation, streams, ocean, air, and even outer space. But individuals and communities are doing things to help protect Earth’s resources and environments.
The demonstration also offers students a chance to engage with some of the NGSS Science and Engineering Practices,
including these: • asking questions • analyzing and interpreting data • constructing explanations • engaging in argument from evidence
Finally, the activity connects to these of the NGSS Crosscutting Concepts:
• energy and matter • stability and change • cause and effect
Green Teacher 119 Page 19
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