Soils

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Soil is the thin surface-layer on the earth made of mineral particles from broken rocks, decayed organic material, living organisms, soil water, and soil atmosphere. It supports plant growth and store…

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Soil supports agriculture, which is the main occupation of humans in many parts of the world. Fertile river valley soils helped early civilizations grow and settle permanently.

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A soil profile is a vertical section of soil from the surface down to the bedrock, showing different horizons with different colours and textures.

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A soil profile normally consists of four horizons: A-Horizon, B-Horizon, C-Horizon, and D-Horizon. The D-Horizon is bedrock and is not part of the soil profile, but it provides the base for the other …

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The A-Horizon is the uppermost soil layer, also called top soil. It contains organic matter and humus. The upper part has more humus, while the lower part has more organic matter. It is also the zone …

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The B-Horizon lies below the A-Horizon and is called subsoil. It contains weathered rock material, sand, silt, and clay. It is the zone of illuviation, where washed-down material collects.

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The C-Horizon is the third layer and consists of weathered parent rock material. The D-Horizon contains unweathered parent rock or bedrock. The D-Horizon is not part of the soil profile, but it forms …

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Soil texture is the mixture of soil particles of different sizes, such as gravel, sand, silt, and clay. It affects water movement, water retention, and ease of ploughing.