The potassium cycle It is the set of chemical, geological and biological processes that make this element circulate on Earth. Therefore it is a biogeochemical cycle, that is to say that potassium (K) circulates constantly in the soil, water and living beings through physical and chemical transformations..
Potassium is one of the most abundant chemical elements in the earth's crust, reaching up to 2.6%. However, not all of that potassium is in available form to be absorbed by plants..
Most of it is unattainable for plants, being embedded in the structure of rocks or between the sheets that form clays. Only less than 1% of potassium forms ions that dissolve in water and can be useful for plant species.
In its cycle, potassium goes through several stages that includes the passage from rocks to the ground (geological stage). Later, it is absorbed by the roots of plants (biological stage) consumed by herbivores and from these it passes to carnivores.
Then, when they all die, the decomposers incorporate the potassium back into the soil (edaphological geological stage) and also the animal excreta reintegrate the potassium into the soil. Part of the potassium present in the soil is carried by water to rivers, lakes and oceans (hydrological stage).
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The potassium cycle goes through three stages:
At the same time, part of the potassium is dragged by the water to a hydrological stage in rivers, lakes and oceans, where it also participates in the biological stage as it is consumed by aquatic organisms..
The main gateway for potassium to the biological world is the plants that absorb it through their roots. Potassium ions (K+) are dissolved in the soil water, which penetrates through the absorbent hairs of the roots (solubilization).
Depending on the plant species, it will absorb more or less potassium. For example, alfalfa can remove up to 322 Kg per hectare of potassium from the soil, while wheat only 12 Kg / Ha.
Once in the plant, the potassium will be used to guarantee the functioning of the plant, its growth, production of flowers and fruits. When the plant is consumed by a herbivorous animal, potassium reaches its body, where it is used and also passes to carnivores who use it as food..
In some cases, especially when dealing with farmyard animals, humans can give potassium supplements to supplement the nutrition. Then, the potassium returns to the soil by two basic routes, the excretions of living beings or when they die.
Urine and feces contain large amounts of potassium, in fact accumulations of bird and bat droppings (guano) are used as fertilizer. Guano provides large amounts of potassium, nitrogen, and phosphorus.
While when living organisms die, their body is decomposed by decomposing organisms and their elements are integrated into these or into the soil. Here the mineralization process occurs, that is, the potassium that is part of the organisms (organic) becomes mineral again. This point is considered the transition from the biological stage to the pedological stage..
The human being actively intervenes in the potassium cycle, since it extracts potassium-rich rock (potash) and collects the guano to prepare fertilizers. These fertilizers are added to the soil to increase the amount of potassium immediately available for crops. Similarly, humans add potassium to food supplements for farm animals.
In this way, there is an anthropic phase in the cycle, in which humans move potassium from one place to another. While accelerating natural processes, by degrading rocks or processing guano, moving it over great distances and applying it.
Potassium is present in the soil in large quantities, although not all of it can be absorbed by plants. Between 80 and 95% of the mineral is in the rocks, in the form of mineral structures, such as feldspars and others.
This cannot be used directly by plants and is known as structural or reserve potassium and potash is one of the rocks that is richest in potassium mineral salts. In general, the release of potassium is usually slow, associated with weathering and erosion processes..
This is the product of the action of agents such as rain and changes in temperature, which break the rock, releasing its mineral constituents. Among these constituents is the potassium that is fixed between the sheets of clays mainly by a process called retrogradation..
In fact, up to almost 20% of the potassium can be fixed in clays, for example on their surface (0.5 to 10% exchangeable potassium). As well as 10 to 20% between the sheets such as micas, being hardly accessible.
Finally, between 0.10 and 0.15% of the potassium in the soil is dissolved by the water in the form of K ions.+. This fraction is immediately assimilable by plants and this assimilable potassium passes back to the biological phase once absorbed by the roots..
In addition, part of the assimilable potassium is carried by rainwater into rivers, lakes and oceans. There it passes to the biological phase when it is absorbed and used by phytoplankton and macroalgae, which are organisms that are part of the food chains of the aquatic environment. Likewise, part of the potassium is deposited integrating sediments at the bottom of lakes and oceans..
These sediments are covered and compacted over millions of years and will be part of the formation of new potassium-rich rocks. These will emerge in geological processes and will be subjected to weathering releasing potassium and thus following the cycle of this element..
The potassium cycle is a process of great importance for life, because it is a fundamental element for the exchange of substances through cell membranes. That is, for any cell in the body to function, it needs to be able to select elements that enter or leave them..
In this process, potassium and calcium are essential for the functioning of this physical-chemical exchange mechanism. In addition, this element helps retain water within the cells so that it does not dehydrate and cause the death of the body.
Potassium is an essential element for various functional processes in the body, such as the functioning of the heart, muscle movements and activity of the nervous system. As well as that each cell is able to absorb nutrients and expel waste.
On the other hand, an excess of potassium also brings problems to the human being, since it can alter the functioning of the heart and kidneys.
Potassium is one of the 3 fundamental macroelements for plant nutrition, along with nitrogen and phosphorus. In fact, after nitrogen, potassium is the element most absorbed by plants.
The main processes of the functioning of plants depend on potassium, such as the opening and closing of stomata, as well as photosynthesis. These are the microscopic openings in the leaves where gas exchange occurs. Similarly, potassium is required for the production of enzymes and other proteins..
Due to the above, potassium is of great importance for agricultural production, so it is added as a fertilizer when it is scarce in the soil.
Thus, the most common fertilizer formula is called NPK, that is, Nitrogen, Phosphorous and Potassium, due to their chemical symbols. In this sense, the obtaining and processing of potassium for the production of fertilizers is a relevant economic activity..
Additionally, potassium has countless industrial uses, since it is used in the production of tempered glass and as an additive in food. On the other hand, potassium superoxide allows the supply of oxygen in submarines and spacecraft.
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