What are the layers of soil and which one contains the most humus?
O Horizon – The top, organic layer of soil, made up mostly of leaf litter and humus (decomposed organic matter). A Horizon – The layer called topsoil; it is found below the O horizon and above the E horizon. Seeds germinate and plant roots grow in this dark-colored layer. It is made up of humus (decomposed organic matter) mixed with mineral particles. E Horizon – This eluviation (leaching) layer is light in color; this layer is beneath the A Horizon and above the B Horizon. It is made up mostly of sand and silt, having lost most of its minerals and clay as water drips through the soil (in the process of eluviation). B Horizon – Also called the subsoil – this layer is beneath the E Horizon and above the C Horizon. It contains clay and mineral deposits (like iron, aluminum oxides, and calcium carbonate) that it receives from layers above it when mineralized water drips from the soil above. C Horizon – Also called regolith: the layer beneath the B Horizon and above the R Horizon. It consi
