Chapter 18: Problem 4

Characterize the principal aspects of each soil horizon. Where does the main accumulation of organic material occur? Where does humus form? Explain the difference between the eluviated layer and the illuviated layer. Which horizons constitute the solum?

Short Answer

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The soil profile is divided into horizons: O, A, E, B, C and R. Organic material primarily accumulates in the O horizon, while humus forms in A horizon. The E horizon is the eluviated layer where leaching occur, and the B horizon, or the illuviated layer, is where these leached materials accumulate. The solum consists of both the A and B horizons.

Step by step solution

Understanding Soil Profile and its Horizons

The soil profile can be divided into several layers, known as soil horizons: O, A, E, B, C and R. These horizons have varying properties such as colour, texture, structure, and chemical composition.

Location of Organic Material and Humus Formation

The O horizon, which is closest to the surface, is chiefly composed of organic material, such as decomposing plant matter, and is where much of the organic material accumulates. Humus essentially forms in the A horizon, also called topsoil. It consists of humified organic matter mixed with mineral particles.

Eluviated and Illuviated Layers

The E horizon, the eluviated layer, is an area of maximum leaching. It is the layer from which materials are being removed and is notable for its paler coloration. The B horizon, also known as the illuviated layer, is where the leachate from the E horizon accumulates. This layer accumulates clay, iron, aluminium, or organic compounds which lend it a darker colour.

Understanding Solum

The solum refers to the combination of the A and B horizons. It is the main region of soil biological activity and root development. The A horizon offers organic matter and nutrients while the B horizon accumulates leached minerals and nutrients from above.

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Characterize the principal aspects of each soil horizon. Where does the main accumulation of organic material occur? Where does humus form? Explain the difference between the eluviated layer and the illuviated layer. Which horizons constitute the solum?

Short Answer

Step by step solution

Understanding Soil Profile and its Horizons

Location of Organic Material and Humus Formation

Eluviated and Illuviated Layers

Understanding Solum

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