Loam -- a type of topsoil prized for agriculture -- is composed of silt, sand and clay.
Soil, a mixture of decomposed organic matter and weathered rock, forms the foundation for terrestrial plant life. The chemical and physical structure of a specific sample of soil is determined by environmental factors such as temperature, weather and geology. Human activity also has an impact on the quality and composition of Earth's soil. In the classroom various types of soils can be blended to conduct a variety of experiments. The experiments listed below require only basic gardening supplies including pots, bean seeds and soil.
Grades K-3
Does the cost of gardening soil affect the size of the plant? This experiment will strengthen your students' understanding of the scientific method and their money skills. For the control, use free dirt that you find around your school or home. Buy two other types of soil of different prices. Plant a seed in each type of soil and measure the height each week. Make sure that each plant receives the same amount of sunlight and water. Compare the cost of the soil to the final growth of the plant.
Grades 4-6
Some plants grow in sandy soils where rainfall is quickly absorbed into the ground while other plants grow in dense soils that do not drain easily. Plant one seed in soil. Plant a second seed in three-fourths soil and one-fourth sand. (Perlite or vermiculite can be used instead of sand.) Plant a third seed in an even mixture of sand and soil. Plant a fourth seed in one-fourth soil and three-fourths sand. Bury the last seed in a pot full of sand. Determine the germination rate for each plant and continue to measure the growth rate for at least two weeks. Compare the growth rate of the seedlings to the amount of sand in the soil.
Middle School
Saltwater intrusion, which results from extracting too much water from underground reserves located near the sea, may have a negative effect on the growth of some plants. Create sea salt solutions at various densities and water the soil with the saltwater solution thoroughly before planting seeds. Continue to water the seedlings with the saltwater solution throughout the experiment. Compare the growth rate of the seedling to the concentration of salt. As an extension, match the salinity of the various seas around the world to determine which geographic areas may be affected the most.
High School
How does the concentration of nitrogen in the soil affect the seedling? Fertilizer strength is often given as three numbers that refer to the concentrations of nitrogen, phosphorus and potassium. A 100-pound bag of fertilizer advertised as 10-15-10 is composed of 10 pounds nitrate, 15 pounds phosphate and 10 pounds of potash, which contains potassium. Create your own fertilizers of various strengths to compare the effects of these elements on the plants' growth. Start with urea -- a fertilizer providing only nitrogen -- which measures 46-0-0. Add various concentrations of a urea solution to the soil before adding seeds to determine the effect of nitrogen on seedling growth rate.
Tags: growth rate, Compare growth, Compare growth rate, each plant, Plant seed