In soil science, which horizons commonly form and what does texture influence?

• A. O, A, E, B, and C horizons; texture controls water retention and nutrient availability
• B. Only A horizon forms
• C. Soils have no horizon structure
• D. Texture has no influence on plant growth

Answer: (A)

Soils develop distinct horizons as organic matter accumulates and minerals are altered by weathering. In many soils you’ll see a sequence from top to bottom: an organic O horizon, a mineral A horizon, an E horizon if leaching has occurred, a B horizon where materials accumulate, and a C horizon of largely unweathered parent material. Texture, the mix of sand, silt, and clay, determines how water moves through the soil and how nutrients are held. Finer textures with more clay and organic matter have higher water-holding capacity and greater nutrient availability because they offer more surface area and exchange sites, while sandy textures drain quickly and hold fewer nutrients. So, recognizing this horizon sequence and understanding texture’s role in water retention and nutrient availability explains why this option best fits how soils form and function.