Which statement best describes what influences soil color?

• A. Organic matter and minerals
• B. Climate
• C. Moisture
• D. Drainage

Answer: (A)

Soil color is determined primarily by what the soil is made of: the amount of organic matter and the mineral content. Dark colors come from organic matter (humus) in the soil, while minerals contribute color through the presence of iron oxides—reddish, yellow, or brown tones from minerals like goethite and hematite. Other minerals, such as carbonates or clay minerals, can lighten or whiten the color. Moisture and drainage influence color as a secondary effect because water changes iron oxidation states and can darken soils or, in poorly drained areas, create gray colors from reduced iron. Climate also plays an indirect role by shaping organic matter accumulation and drainage patterns, but the direct color drivers are organic matter and minerals.