PS U6 L3 Soil Horizons
Soil Profile sequence of horizons from the surface down through the horizons to the parent material
Soil Horizon layer approximately parallel to the soil surface, with characteristics produced by soil forming processes. If you dig very deeply into the soil, you will see that soil lies in distinct layers. These layers are called soil horizons.
3 Major Horizons A = dark colored zone of organic matter accumulation lying on the surface of the soil profile. It is generally darker than the lower layers. The A horizon is where life in the form of plant roots, bacteria, fungi and insects are most abundant. It is often called “top soil”. B = This horizon lies just below the A horizon and is often called the sub-soil. It is often finer in texture than the A horizon. It is usually higher in clay and has more pronounced structure than the A horizon. C = This horizon is located below the “true soil”. This horizon is often called parent material. It has not been weathered enough to be called soil. This zone may show an accumulation of calcium and magnesium salts causing it to be light in color.
AC Horizon designation means = What??
O Horizon Organic horizon of decomposed and undecomposed organic matter. Present in forested soils. Absent in grassland, cultivated and many other soils.
E Horizon Mineral horizon that is usually light in color due to the leaching out of iron, aluminum, clay and organic matter. Typically present in forested soils.
R Horizon Underlying consolidated bedrock such as granite or shale. Absent under many soils
Ap = What?? ??
Let’s Put it all in order B C R
Soil Profile Changes Additions: Materials such a fallen leaves, wind-blown dust, or chemicals from air pollution that may be added to the soil. Losses: Materials may be lost from the oil as a result of deep leaching or erosion from the surface.
Soil Profile Changes cont. Translocations: Materials may be moved within the soil. This can occur with deeper leaching into the soil or upward movement caused by evaporating water. Transformations: Materials may be altered in the soil. Examples include organic matter decay, weathering of minerals to smaller particles or chemical reactions.