structural:reformatting, stylistic:tone
Soil

The thin top layer of the Earth's crust on land is largely made up of soil colored different shades of brown. Good soil is composed of about forty-five percent minerals, twenty-five percent water, twenty-five percent air, and five percent organic material, living and dead. Half the color of soil comes from minerals it contains; soils containing iron turn yellowish or reddish as the iron oxidizes. Manganese, nitrogen and sulfur turn brownish or blackish as they decay naturally.

Rich and fertile soils tend to be darker in color; the deeper brown color of fertile soil comes from the decomposing of the organic matter. Dead leaves and roots become black or brown as they decay. Poorer soils are usually paler brown in color, and contain less water or organic matter.