![]() Horizon is a distinct layer of soil, approximately parallel with the land surface, whose properties develop from the combined actions of living organisms and percolating water. The idea of Horizon and Soil Horizons are slightly different. ![]() These layers are called horizons in soil science. It doesn’t just help in determining the properties of the soil in general, but also helps in understanding the geological events of the past.Do you ever dig down deep into any soil? If you did so, you may have followed different colors and layers in there. Study of the soil horizon is the first and one of the most crucial steps when studying the soil taxonomy for a particular region. When it comes to soil classification, the systems put to use differ from one region to another in the United States, for instance, it’s the USDA soil taxonomy. In some regions, the bedrock is located just a few inches below the surface, and in some, it is found several feet below. It is very difficult to dig through this layer. Unlike the horizon above, this horizon does not comprise rocks or boulders, but instead is made of continuous mass of bedrock. The R horizon is basically the deepest soil horizon in the soil profile. As plant roots do not reach this layer, the C horizon is typically devoid of organic matter. That explains why the rocks in this layer haven’t changed much since their origin. ![]() This layer is least affected by weathering as it lies deep within the soil and is inaccessible to the soil-forming agents. It is considered the transition layer between soil and parent material. The C horizon is mainly made of large rocks or lumps of partially broken bedrock. Plant roots may reach this layer, but the chances of this are pretty less, and therefore, its humus content is very low. Though this layer has a high mineral content as compared to the topsoil, the chances of some organic matter reaching this layer as a result of the leaching process cannot be ruled out. It is usually reddish or brown in color, which can be attributed to the presence of the iron oxide and clay. The B horizon is rich in clay and minerals like iron or aluminum. The E horizon in rarely seen in a cultivated area where it is mixed with the A horizon because of plowing activity. The soil particles of this layer are larger in size than those in the A horizon, but smaller than those in the underlying B horizon. It is poor in mineral and clay content as these are lost to the lower layers in the process of leaching and therefore, it is also called the layer of eluviation (leaching). The E horizon, which lies between the A and B horizons, is known by its characteristic light color, and its sand and silt content. ![]() As most of the biological activities take place in this layer, it is often referred to as the ‘biomantle’. Even the soil organisms, like earthworms, fungi, and bacteria, are mainly concentrated in this layer. ![]() It is this layer where seeds germinate and roots grow. Similarly, the soil particles in this zone are smaller and finer compared to the lower horizons of the soil. As it lies just below the O horizon, this layer also has some amount of humus in it and therefore, it is darker than the layers below. The A horizon is the topmost layer of the mineral soil. ![]()
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