Soil
Soil is earth’s superficial covering. Soil consists of minerals like clay, sand or bits of rock, decaying parts of plants and animals, water and air. It provides Earth’s rocky skeleton with a loose covering which varies widely from place to place. The composition of the soil is contingent upon the kinds of geological materials from which it is made, the kind of vegetation growing on the soil and by human activities which may make artificial alterations to the soil. Plants take root and grow in soil, animals graze and make their homes in soil, and humans plant crops for food in the soil and build on the soil.
Plants rely on the soil to get the water, nutrients and minerals they need. They grow roots to get to the layer of soil containing the right conditions for growth. Soil is found to have three different layers. The top layer or topsoil, is rich in organic matter. The second layer, is mostly organic but may also contain some rocks. The third layer is comprised mainly of rock which lies under the soil.
Soil holds water and keeps it from evaporating. The availability of water from the soil is critical in the productivity of the soil. How long and how much water is held depends on the type of soil. Clay soil, which is a heavy compact soil, holds water for a longer period of time while a sandy soil is usually incapable of holding enough water for plant growth.
Plants are provided with nutrients from decaying plants and animals found in the soil, while the crushed rocks provide the minerals needed for plant growth. Worms and insects found in the soil help in the breaking down of this decaying material, thus enriching and aerating the soil. These materials after having passed through the bodies of these natural decomposers change the texture and quality of the soil.
Scientists take samples of soil and group them according to their general characteristic. They draw pictures of the land which they call soil profiles. The picture emphasizes the properties of the soil that can be seen, felt or measured.
Soil undisturbed by human tillage or deforestation preserves its balance of humus by decomposition and decay of plant and animal bodies thereby allowing a wide variety of different plant, animal and insect species to exist.
Objectives
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1. To understand soil is made of many different things such as minerals like clay, rock and sand, decaying plants and animals, air, and water.
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2. To separate and identify what different types of soil are made of.
Materials
Soils from several different locations, jars with lids for each kind of soil, labels, marker, water, and large spoon.
Procedure
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1. Make two columns on a large sheet of paper. Label one column before and the other after.
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2. Ask the children what they know about soil. Write their responses in the “before” column.
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3. Show the students the bags of soils and other materials. Explain that they will be doing an experiment which will show what each of these soils is made of.
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4. Place 1/4 cup of soil in each jar and fill it with water. Secure the lid and shake the jar well to mix the soil and water. Label the jars with the soil type. Set them aside for a few days so they can settle into different layers.
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5. Have the children discuss what the different layers in each jar are made of. Let comparisons be made between each jar.
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6. Divide the children into groups and allow them to draw their soil’s proflle in their eco-joumals and label the different layers seen.
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7. Let the children discuss which type plants would grow best in each soil.
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8. Review with the children what they know about soil. Record their responses under “after” in column two.