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What is the source of the chemicals found in the soil? Students should think about the materials they identified in their investigation of a soil mixture. The various rocks and minerals, the organic material that is present in the soil, and even the rain that falls on the soil all contribute to the types of chemicals in that soil sample.
Most soils take a long time to form. They form from rocks and sediments (parent material) that have disintegrated and decomposed through the action of weather and organisms (a process called “weathering”). The rate of soil formation is largely controlled by rainfall, temperature, and the type of parent material. High temperature and abundant rainfall speed up soil formation, but in most places a fully developed soil that can support plant growth takes hundreds of thousands of years to form. (From AGI Environmental Awareness Series: Sustaining our Soils and Society p8).
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