Portal:Ecology/Selected picture/3
Credit: Lynn Betts, USDA Natural Resources Conservation Service
Topsoil is the upper, outermost layer of soil, usually the top 2 inches (5.1 cm) to 8 inches (20 cm). It has the highest concentration of organic matter and microorganisms and is where most of the Earth's biological soil activity occurs. Pictured: Terraces, conservation tillage, and conservation buffers save soil, control erosion and improve water quality on this Iowa farm. 1999.