what is the main layer oo soil?explain in points and in the definition
Answers
Answer:Soil is made up of many layers. These layers are often called horizons. Depending on the type of soil there may be several layers. There are three main horizons (called A, B, and C) which are present in all soil.
Organic - The organic layer (also called the humus layer) is a thick layer of plant remains such as leaves and twigs.
Topsoil - Topsoil is considered the "A" horizon. It is a fairly thin layer (5 to 10 inches thick) composed of organic matter and minerals. This layer is the primary layer where plants and organisms live.
Subsoil - Subsoil is considered the "B" horizon. This layer is made primarily of clay, iron, and organic matter which accumulated through a process called illuviation.
Parent material - The parent material layer is considered the "C" horizon. This layer is called the parent material because the upper layers developed from this layer. It is made up mostly of large rocks.
Bedrock - The bottom layer is several feet below the surface. The bedrock is made up of a large solid mass of rock
Explanation:
Answer:
Soil is the material found on the surface of the earth that is composed of organic and inorganic material. Soil varies due to its structure and composition. Learn about the different types of soil and soil structures in this video lesson.
What Is Soil?
Chances are that you haven't thought a lot about the soil under your feet, but you may be surprised at the complexity of soil. Soil varies in its composition and the structure of its particles, and these factors are closely examined by farmers, who need appropriate soil for planting crops, as well as engineers who may need to understand how soil is going to hold up under different demands. Soil is also vitally important to the sustainability of an ecosystem because it serves as the natural medium for the growth of vegetation. In this lesson, you will discover just what soil is and which factors are looked at when determining the structure and the types of soil.
So, what exactly is soil? Soil can be defined as the organic and inorganic materials on the surface of the earth that provide the medium for plant growth. Soil develops slowly over time and is composed of many different materials. Inorganic materials, or those materials that are not living, include weathered rocks and minerals. Weathering is the mechanical or chemical process by which rocks are broken down into smaller pieces. As rocks are broken down, they mix with organic materials, which are those materials that originate from living organisms. For example, plants and animals die and decompose, releasing nutrients back into the soil.
Soil Profile and Soil Horizons
Now, if you look down at the soil under your feet, you cannot tell very much about that soil. So, when you study soil, it's helpful to grab a shovel and dig a hole that is big enough to reveal a vertical section of soil that ranges from the surface to the underlying rock, referred to as a soil profile. The soil profile is somewhat like the soil's fingerprint, and it will differ from other soil samples based on factors like its color, texture, structure and thickness, as well as its chemical composition.
Each layer of a soil profile is referred to as a soil horizon. These horizons are identified by letters. Horizon A is the upper layer, closest to the surface. You can think of this horizon as the topsoil. In fact, you can use this as a memory jogger to help remember the order of the horizons. The letter A is at the top of the alphabet and refers to the topsoil layer. As you move deeper into the layers of the soil profile, you have horizons B and C, giving us the three main horizons.
Types of Soil
There are three basic types of soil: sand, silt and clay. But, most soils are composed of a combination of the different types. How they mix will determine the texture of the soil, or, in other words, how the soil looks and feels.
One type of soil is sand. Sand within soil is actually small particles of weathered rock. Sand is fairly coarse and loose so water is able to drain through it easily. While this is good for drainage, it is not good for growing plants because sandy soil will not hold water or nutrients.
Silt is another type of soil. Silt can be thought of as fine sand, and it will hold water better than sand. If you were to hold a handful of dry silt in your hand, it would feel almost like flour. If you were to add water to the silt in your hand, it would do a fair job of holding the water and feels slick and smooth.
Clay is very fine-grained soil. Its particles are even smaller than silt, so there is very little space between the fine grains for air or water to circulate. Therefore, clay does not drain well or provide space for plant roots to flourish. If you were a farmer, you would not want your field to be mostly clay. However, if you were a potter, you would think clay was the best type of soil. When moisture is added to clay, it can be molded into shapes, such as a pottery bowl or a building brick.
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