The Food Formula
Time Duration
2 sessions a week a part; 20 - 30 minutes each session
Purpose
Students will investigate what soil types are best for a given crop.
Kentucky Academic Standards
NGSS
3-LS4-3 Construct an argument with evidence that in a particular habitat some organisms can survive well, some survive less well, and some cannot survive at all.
5-PS1-3 Make observations and measurements to identify materials based on their properties
Materials
Soil samples (sand, clay, humus, local soil)
4 baking pans or plastic containers for planting seeds in the soils
Ryegrass seeds
Prepare
Discuss with students the background information on soil in the digital presentation.
Procedures
Obtain sand, clay, humus, and local soil samples and place them in the four containers. If students work in smaller groups, you may need to duplicate materials.
Discuss the properties of each (color, odor, texture dry, and texture wet). For example, sand has the largest particles and is gritty; humus has medium, soft, and silky particles; clay has the smallest particles and gets sticky when wet. The local soil may contain a mixture. You may conduct the “Dirt on Soil” lesson to determine the type of soil you have collected, or your local county extension office may be able to give you more exact information about your soil’s composition. Have students hypothesize which soil best grow the ryegrass seeds based on what they learned in the digital presentation and video.
Plant ryegrass seeds (about 20) in each container. Mist or lightly water soil until damp. Place in a sunny location. Keep seeds moist and observe daily. Keep other variables constant by using the same size/type containers, the same amount of soil, sand, humus, or clay, and the same amount of water.
After seeds have grown a few inches, discuss which type of material produced the best ryegrass crop and why. Students should explain the effects of the different variables. For example, clay is thick and sticky, which is tough for roots to grow through. Sand may do OK but will not hold water in as well. Depending on its richness, your local soil may or may not have been the best. Humus should do well because of its richness in nutrients and texture. Particles need to be loose enough for roots to grow, but not so loose water will run through too rapidly and not have time to soak roots.
Discuss other variables. What if you changed the type of plant grown in the soil? Would you get the same results? What about different amounts of water? Some plants adapt to their ecosystems, including soil type and water availability. Most farmers grow crops that perform well in their farms’ soil types with little need for change. Organic matter and nutrients can be easily added, but changing soil structure and composition may be costly.
