The horizons of the soil.
(Edited)
Dear readers, in this publication we will give a brief description of the horizons or soil layers and how they can be observed in agricultural fields. Since, as mentioned in previous articles, it is necessary to know the physical characteristics of the soil such as texture to know for example water retention levels and aeration. Technicians and/or farmers sometimes make a hole in the ground that carry by name calicata and are usually made with the following dimensions 2x2 meters, This is done with the intention of knowing the different layers that make up the agricultural soil and from there take some samples to determine some characteristics.
When a calicata is made you can observe the layers of the soil at different depths and through its walls you can identify in the soil the color differences of each layer. These layers individually are technically known as horizon and together we talk about the profile of the soil because we can see some of its characteristics.
Below, we will describe the different horizonsthat can be visualized in a soil profile, taking into account the experience in the field and the socialized by some researchers such as Casanova (1996); FitzPatrick (1996) and Molina (2010). ¡ Let’s get started!
To begin with it is important to mention that each horizon can have different thicknesses and colors also depending on the ecosystem in which they are located, taking into account that temperature and humidity greatly influence the decomposition of organic matter. We mention organic matter because the topmost layer of the soil is known as mulch and/or "Horizon O", on this horizon is where the highest proportion of soil organic matter is found, due to the decay that occurs from the leaves of the trees; in tropical areas with high temperatures and high humidity levels decomposition increases and it is common to observe this layer with a dark color.
The layer that follows the horizon O is known as "Horizon A" which according to Molina (2010), is formed with the mixture of decomposed organic matter and certain particles of minerals of the soil, forming a looser substrate compared to the deeper layers. For its part, Casanova (1996), mentions that it is the layer where the most microorganisms are concentrated and where a high percentage of the soil roots develop. That is, from our point of view is one of the most important layers, for plants to develop the radical system and maintain an adequate amount of nutrients, for this, you must maintain excellent levels of organic matter.
After horizon A in some soils a thin layer is formed that is formed from the washing of organic matter and nutrients from horizon A and becomes a lighter color, then this layer is formed another known with the name "Horizon B", FitzPatrick (1996), notes that this horizon is the real soil where approximately 20% of the soil organic matter accumulates, in addition the presence of the mineral fraction such as clay, sand and silt generating a mixture of said elements.
Finally, in the depths of the ground, there are the Horizon C and D as seen in the image of the horizons, the Horizon C formed by a material that has undergone a low disintegration process, in this area there is no biological activity due to the low or no presence of organic matter and unfavorable conditions and the Horizon D which is the mother rock.
| final considerations |
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Dear readers, it was possible to show how in the soils of natural ecosystems begin to form layers and/or horizons by the disintegration of the original material present in them and the accumulation and decomposition of organic matter thanks to the activity of various microorganisms. The importance of natural processes and the fundamental role that each component plays in ecosystems are also observed.
On the other hand, the thickness of these horizons will depend as mentioned above on the ecosystem, they can measure from centimeters to meters, of course it is logical that in tropical areas the first layers are thicker, by the accelerated decomposition of organic matter from trees and animals.
It can also be inferred why when soil sampling is performed on pasture surfaces, it is collected between the first 5 and 15 centimeters of the soil, since, said plant has superficial roots, which will take advantage of the first horizons during its establishment and development, in this case the percentage of organic matter becomes an important indicator when making an analysis.
| bibliographic references |
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- Molina, M.(2010). Fundamentals of natural factors and agricultural production. UNESUR. Venezuela.
- FitzPatrick, E. (1996). Introduction to soil science. Trillas: Mexico.
- Casanova, E.(1996). Introduction to soil science. Central University of Venezuela.
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Thanks for this nice blog. I have a question on it. Do you have information on how soil profiling is made? Is it enough to sample the soil up to a given depth and analyse what comes out of it?
Thanks in advance for your answer!