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The Scoop on Dirt Soil • Soil is made up of weathered rock, including gravel, sand, and silt. • Topsoil comes from subsoils and rocks beneath the surface. • Topsoil takes thousands of years to form. Photo courtesy of USDA NRCS What is a Natural Resource? • Something that people can use in order to live. • Something that is not man-made, but has formed naturally over hundreds, thousands, or even millions of years. • Something that cannot be easily replaced once it is used up. Can we say that topsoil is a valuable natural resource? • How is it used by people in order to live? • Can we make it in a “topsoil factory”? • If we use it up, can we easily get more? How can we lose topsoil? • Water can wash it away with rain and flooding. • Wind can blow it away. • This process is called erosion. Photo courtesy of USDA NRCS How can we conserve topsoil and prevent erosion? • Roots of plants help to hold the topsoil in place. • Where can we put plants so that their roots can hold the soil? – – – – On hillsides. Along rivers and streams. Around the edges of fields. Can you think of a place? Photo courtesy of USDA NRCS Soil Types • Soil is made up of organic and inorganic substances. Soil Types • Soil is made up of organic and inorganic substances. Organic means substances that were once living such as leaves, twigs, remains of animals, and microorganisms. Soil Types • Soil is made up of organic and inorganic substances. Inorganic means nonliving substances such as rocks and gravel. We can group soil into three types: We can group soil into three types: • Clay (or clayey soil) We can group soil into three types: • Sand (or sandy soil) We can group soil into three types: • Loam (or loamy soil) We can group soil into three types: • Clay (or clayey soil) • Sand (or sandy soil) • Loam (or loamy soil) Clay • Clayey soil is made up of tiny particles that are too small to separate. • Clay feels powdery when dry and sticky and slimey when wet. • Clay forms hard clods when dry and sticky clumps when wet. • Because the particles are so small, water cannot drain well from clay. Photo: Martha Rogers Sand • Sandy soil is made up small bits and pieces of rock and smaller particles called silt. • Sand does not stick together when it is wet or dry. • Sand particles are loosely packed and water drains through it quickly. Photo: Martha Rogers Loam • Loamy soil is a mixture of sand, clay, and organic materials called humus. • Loam does not become sticky when wet, nor is it powdery when dry. • Because it contains humus, loam is a rich soil that holds water and also drains well. Photo: Martha Rogers Let’s do an experiment to see which soil would be best for growing plants! Photo: Martha Rogers