Soil chemistry is the branch of soil that deals with the structure, properties, and chemical reactions. As the soils are a heterogeneous mixture of organic and inorganic matter.
- The darker soils are found where the soil consists of heavy deposits of organic matter. The presence of a large quantity of organic matter makes the soil darker near the surface.
- The presence of humus in the top layer of soil is essential for the formation of thick and dark colours.
Hence the option A is correct.
Learn more about Color and soil chemistry.
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