The Scoop on Soil By Laura G. Smith

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¹     What do earth worms, fresh vegetables, and fragrant flowers all have in common? They all rely upon soil for their existence. Actually, all forms of life on earth depend upon the soil, either directly or indirectly.
 
²     Plants are rooted in soil and receive nourishment from it. Animals get their food from either the plants rooted in the soil or from other animals that eat the plants. Humans rely upon the soil to nourish the crops that produce our fruits and vegetables. The soil also provides shelter for many kinds of animals.
 
³     Soil is made up of mineral and organic particles, other plant and animal matter, air, and water. There are many different kinds of soils, each having its own color and texture. It takes a long period of time for soil to form, and it is destroyed very easily. It's important that we conserve this valuable natural resource so it can continue to support life.
 
⁴     Soil formation begins with a process called weathering. Weathering involves the physical disintegration and chemical decomposition of rocks, minerals, and immature soils at or near the earth's surface. Weathering also initiates the erosion of rock, causing changes in the surface layers of the Earth.
 
⁵     As weathering occurs, soils are formed taking on different characteristics based on five environmental factors. These factors include (1) kinds of parent materials (rocks or other material that is broken down), (2) climate, (3) land surface features, (4) living organisms, and (5) time.
 
⁶     Parent materials contain different types of minerals that impact the make up of the soil that is eventually formed. This will affect the type of plants that are able to grow in the soil. For instance, azalea shrubs grow better in soil that is rich in iron.
 
⁷     Climate affects the physical and chemical activity in the soil. For example, cold weather and dry air cause the physical breakdown of rock materials. High temperatures and humidity are more likely to cause chemical breakdown and decay of materials.
 
⁸     Land surface features (or topography) also influence soil development. Soil that is on the side of a hill will be eroded (washed away) by rain, leaving the rock below exposed to weathering. These soils have less time to form and therefore develop less than soils on flat surfaces. The lay of the land also affects the temperature of the soil, causing different levels of chemical breakdown of the particles. For instance, the soil on a hillside that receives direct sunlight most of the day would absorb far more heat than the shaded soil beneath a large maple tree.
 
⁹     Living organisms and organic material (materials that come from plants or animals) help soil develop, and they also protect it from erosion. The death and decay of plants and animals add organic material to the soil, which helps to support new organisms. Soils that have a healthy plant cover can better resist erosion.
 
¹⁰     The amount of time soil needs in order to develop varies according to the other four factors we have discussed. Young soils may develop in just a few days from sediments left from floods or from volcanic ash. Other soils may take thousands of years to form.
 
¹¹     There are three basic layers of soil. The top layer is called topsoil and is made up of tiny rock materials formed by weathering. Topsoil usually contains humus, which is formed from the decay of dead animals and plant parts. Humus enriches the soil and gives it a gray-black color.
 
¹²     Most plants grow in this top layer, and it is also home to such animals as ants, moles, and earthworms. These tiny creatures play an important role in the formation of the lower soil layers as they dig tunnels that create spaces for air and water to penetrate. Bacteria, fungi, and one-celled animals also live in topsoil. Some are responsible for the decay of dead plants and animals. Some bacteria also add nitrogen to the soil. Plants need nitrogen and other elements, such as potassium and phosphorus, to grow.
 
¹³     Wind and water can carry topsoil from one place to another. Water also washes minerals out of topsoil and carries them down into the subsoil. This process of removing minerals from topsoil is called leaching.
 
¹⁴     The second layer of soil, called subsoil, contains minerals leached out of topsoil by water. It also contains pieces of weathered rocks. Though there is no humus in subsoil, some plant roots grow down into it. Subsoil is lighter in color than topsoil.
 
¹⁵     The substratum is the third soil layer. It is mostly large rock pieces that are being worn down by weathering. As these rocks are broken into smaller and smaller pieces, they form new subsoil.
 
¹⁶     Beneath the three layers of soil there is solid rock called bedrock that is part of the earth's crust.
 
¹⁷     The study of different soil types is called pedology. Scientists study the soil for several reasons, one of the most important of which is to help farmers know how to select and support the crops on their land and to maintain fertile, healthy ground for planting. Understanding soil is also important in engineering and construction. Soil engineers perform detailed studies of the soil before building roads, houses, and industrial and retail structures.
 
¹⁸     In years past, erosion has destroyed soils around the world because people were not careful to treat it as a valuable, nonrenewable natural resource. In recent years, farmers and other experts have been finding ways to practice what is called soil management. In order to reduce erosion, farmers use techniques such as planting grasses to protect the soil from rain between crop-growing seasons. They can also plant crops on the slope of a hill instead of in rows that go up and down.
 
¹⁹     Other things that cause soil loss are the removal of trees from the forests and overgrazing by livestock. Humans also cause damage to the soil when chemical pesticides are used or when liquid and solid wastes are carelessly allowed to leak into the ground.
 
²⁰     With the world's population now reaching 6 billion people, humans will depend more than ever on soil. Without it, there would be no crops for food, no forests, flowers, or grasslands. As people become more and more aware of soil's importance, many changes are being made in an effort to better protect this valuable resource.

Copyright © 2019 edHelper

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Name _____________________________

Date ___________________

The Scoop on Soil

1.   What is the process that begins the formation of soil?   Rainfall   Erosion   Weathering   Decomposition	2.   What are the five factors that determine the characteristics of any particular soil?
3.   Another term for "land surface features" is:   Topography   Meadow   Leaching   Soil management	4.   Most plants grow in which layer of soil?   Humus   Substratum   Topsoil   Subsoil
5.   How do high temperatures and humidity tend to affect the formation of soil?   It makes the soil darker in color.   It causes chemical changes and decay of materials.   It breaks down large rock materials.   It attracts worms that like the heat.	6.   Why is pedology important to our world?

 

Name _____________________________

Date ___________________

The Scoop on Soil

7.   Wind and water sometimes carry topsoil from one place to another. A word that describes this process is ________________.   Decay   Flow   Substratum   Erosion

8.   Ants, daisies, squirrels, tomatoes, cows, birds, and people all rely on soil for their existence.   False   True

 

The Scoop on Soil - Answer Key

1    Weathering
2  (1) kinds of parent materials, (2) climate, (3) land surface features, (4) living organisms, and (5) time.
3    Topography
4    Topsoil
5    It causes chemical changes and decay of materials.
6  It provides important information to farmers so they'll know what crops to grow and how to best support them. It provides needed information for engineers in designing and building structures.
7    Erosion
8    True