Land Use and Its Effects Flashcards
1 what is soil
What is soil?
You’ve just studied the forces that weather and erode rocks. But the upper layer of the earth’s surface is not merely rock. It is soil. Soil is a mixture of nonliving and living parts, including the following:
organic pieceswrock pieces, decayed material, water, and air
living partswfungi, worms, bacteria, and other microorganisms
The living parts and the decayed material make up the humus, which gives a sweet smell to the soil and provides nutrients for plants.
soil vs regolith
While soil has both living and nonliving parts, regolith has only nonliving parts consisting of tiny pieces of rocks. Regolith is sterile with no life or decayed matter. The moon’s surface is regolith, which consists of tiny fragments of rock, dust, and volcanic glass that have been weathered by impacts from micrometeoroids over billions of years.
2 soil is complex
Soil is complex.
Imagine a jar of marbles of various sizes. A jar of soil would be like that. The marbles represent the rock pieces. Three types of rock pieces make up soil:
Sand is the largest particle (less than 1/16 in.).
Silt particles are smaller.
Clay particles are smaller still. They are so small that they stick together when wet.
The various rock particles stick together and form clumps, or aggregates, that vary in size. The wet clay particles and humus form sort of a glue that holds the clumps together.
Like the marbles in the jar, the aggregates have spaces between them called pores. The pores contain air and water and form tunnels, through which groundwater flows.
3 all soil is not the same
All soils are not the same.
Soils have different properties such as composition, color, smell, and texture.
Composition is the percentages of sand, clay, and silt.
Color depends on the amount of air and water mixed into the soil. Red and brown are good, while gray and olive have too much water. Black has little or no air.
Red and brown soils have a sweet smell, while black soils smell like rotten eggs.
How soil feelswgritty, flourlike, or stickywis determined by its composition. Texture determines how water will be held in, and flow through, the soil. For example, loam is an equal mixture of sand, silt, and clay.
Soil characteristics can help determine how land is used.
Soil characteristics can help determine how land is used.
Soil properties are important in considering how the land should be used. For example, if soils have adequate moisture and air, they may be good for farming. The composition may vary, which will determine the types of crops that can be grown. If soils contain too much water and are black, they would not support crops. But they might be classified as wetlands, which provide good wildlife habitats. Finally, soils that compact well may be good for constructing buildings, while those with high sand and gravel contents would be better suited to be mined for construction materials, such as the ingredients for concrete.
Water and air flow over the soil and erode it.
Water and air flow over the soil and erode it.
Food grows in soil; therefore, soil is considered an important natural resource. Soil is the product of weathering and is subject to erosion. The flow of water is the most significant eroding factor in most climates. (In deserts, however, wind is the major erosional force.) Soil erosion by water reults in the following characteristic features of the land:
small channels or rills in the surface large gullies accumulated soil at the bottom of slopes sediments in lakes, rivers, and streams exposed underlying subsoil of different color
Inappropriate land use hastens soil erosion, which affects land use.
Inappropriate land use hastens soil erosion, which affects land use.
Improper land-use practices increase erosion. First, plowing fields parallel to the slope of a hillside creates channels for water to flow down. Second, removing vegetation eliminates plant roots, which would have helped anchor the soil in place. Third, toxic substances pollutes the land, kills living things in the soil, and renders the soil infertile. Fourth, extensive development and paving of the land prevent water from penetrating the underlying soil, creating avenues for runoff.
A good conservation plan can reduce the flow of water over the soil.
A good conservation plan can reduce the flow of water over the soil.
Most soil conservation plans attempt to minimize the avenues for water runoff.
Contour plowingwHillsides are plowed across the hill instead of up and down, which reduces water flow down the hillside and slows the runoff.
TerracingwWhere contour plowing is impractical, cutting terraces into the hillside has the same effect as contour plowing.
Maintaining ground coverwLeaving harvested plant material on the surface creates a natural barrier to water runoff.
Good land use requires good planning.
Good land use requires good planning.
Many factors should be considered when deciding how land will be used. A soil survey reveals the characteristics of the soil, which can help determine whether the land is suitable for agriculture or for something else. If farming is to be done, the crops should be matched to the soil type to minimize the need for irrigation. As much ground cover as possible should be maintained. Natural areas or greenways prevent soil erosion and provide habitats for wildlife. Economic needs and aesthetics may also be major considerations, especially for industrial or recreational development.
Good land planning requires input from scientists, politicians, business leaders, and citizens.
Soil influences land use, which affects soil.
Soil influences land use, which affects soil.
Soils are complex mixtures of living and nonliving parts. Soils vary in composition, moisture, aeration, color, and texture. The properties of soils help determine how the land should be used and what crops might be grown on the land.
Water and air flowing over the land erode the soil. Soil erosion can degrade the properties of the soil and change the possible use of the land, such as make it infertile for farming. Most methods of soil conservationwcontour plowing, terracing, using windbreaks, and maintaining ground coverware aimed at minimizing the flow of air and water over the land, thereby preventing soil erosion.
