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- Soil horizons are distinguished by various properties, including color, texture, mineral content, and organic content. The vertical arrangement of horizons is known as a soil profile. Soil profiles can help distinguish soil types, and can also be used to predict soil fertility.
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Aug 11, 2022 · Soils are classified into one of 12 soil orders based on soil horizons, how they form, and their chemical compositions. For example, Mollisols (figure \(\PageIndex{f}\)), which are found in temperate grasslands, have a thick topsoil rich in organic content.
Factors that affect soil formation include: parent material, climate, topography, biological factors, and time. Soils are classified based on their horizons, soil particle size, and proportions. Most soils have four distinct horizons: O, A, B, and C.
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Review your understanding of soil formation, soil horizons, and erosion in this free article aligned to AP standards.
•Soil is the loose surface material that covers most land. Soil is a mixture of minerals, organic matter, living organisms, gases, and water.
•Soil is produced from rocks, or parent material, as a result of weathering. Weathering describes the breakdown of rocks by physical, chemical, or biological processes. Particles that break away during weathering are transported and deposited as layers of soil on land, or layers of sediment underwater.
•Soils have layers called horizons. Soil horizons are distinguished by various properties, including color, texture, mineral content, and organic content.
•The vertical arrangement of horizons is known as a soil profile. Soil profiles can help distinguish soil types, and can also be used to predict soil fertility. The generalized soil profile below includes four major soil horizons: O, A, B, and C:
•The O horizon, or organic horizon, is made up mostly of organic matter such as leaf litter and decomposed plant material. This layer can be thin, thick, or not present at all, depending on how a soil forms.
•The A horizon, or topsoil, is the upper layer of soil in which plants have most of their roots. It has a high concentration of organic matter and microorganisms. So, this layer and the O horizon are often the most nutrient-rich and productive layers in a soil profile.
Soils are named and classified based on their horizons. The soil profile has four distinct layers: 1) O horizon; 2) A horizon; 3) B horizon, or subsoil; and 4) C horizon, or soil base ( Figure 31.7 ). The O horizon has freshly decomposing organic matter—humus—at its surface, with decomposed vegetation at its base.
Feb 17, 2023 · The soil is the topmost layer of the earth’s crust consisting of air, water, inorganic minerals (rock, sand, clay, and slit), and organic matter (dead plants and animals). It forms the source of food for plants. It provides shelter for many animals such as insects, centipedes, burrowing animals, microorganisms, and many others.
Describe how soils are formed. Explain soil composition. Describe a soil profile. Plants obtain inorganic elements from the soil, which serves as a natural medium for land plants. Soil is the outer loose layer that covers the surface of Earth. Soil quality is a major determinant, along with climate, of plant distribution and growth.
