Nitrogen in agricultural ecosystems

Nitrogen is a mineral element that in the world of agriculture is essential for the growth and development of plants, when a plant for example grasses has the appropriate amounts of nitrogen improves some morphological characteristics of these as the seeding in species that are established in this way, it also influences the height of the plant. If, on the contrary, an insufficiency of this element is found, a yellowish color can be seen in the leaves and a plant with poor growth.

In agricultural agroecosystems it is important to take into account that, despite the importance of this nutritional element, there may be a deficiency of it because this element is not part of the parent material from which the soil originates, the largest percentage of nitrogen is available in the atmosphere and thus cannot be used by plants, in addition to the deficiency that may exist in the soils of this element, there is also the possibility of it being lost to the atmosphere through volatilization or by leaching due to the excess water that may exist at any given time.

For the aforementioned, it is important to mention that nitrogen can be fixed to the soil through a natural process carried out by some bacteria, some are freely in the soil and others perform symbiosis with the roots of some plants such as those belonging to the legume families, this element can also be obtained through a recycling of nutrients that is what we refer to, for example, the leaves of some trees that once they fall to the ground are decomposed by efficient microorganisms and mineralize this element so that it can be used by crops. Most of the processes of obtaining this element with the exception of the one obtained through industrialized processes obtaining synthetic nitrogen fertilizers such as urea.

The use of synthetic nitrogen fertilizers excessively can cause high environmental costs, among them is the pollution of waters through the leaching process that consists of washing this element accumulating in water reservoirs, decreasing the biodiversity of aquatic ecosystems and the excessive propagation of aquatic plants. In addition, according to several researchers, with the excess of synthetic fertilizers, nitrates are transformed into nitrites, which when absorbed by humans cause negative health effects.

Dear readers, in recent years, with the approach of sustainable agriculture, soil microorganisms have begun to be taken into account as fundamental elements of many natural processes, including nitrogen fixation, since there are free-living or associated bacteria that can fix this element. Microorganisms benefit from nitrogen fixation by being able to use nitrogen from the air and incorporate it into compounds essential for their growth and development. According to Tejera (2005), it is only when nitrogen-fixing microorganisms die that nitrogenous organic compounds are released into the environment, which are transformed into nitrate and ammonium, which can already be assimilated by plants or other microorganisms.

The interactions and the association between the microorganism and its host plants, as well as the nitrogen fixation process, can be inhibited by the presence in the soil of high levels of synthetic fertilizers that progressively begin to alter the soil characteristics such as pH until having a soil with little biological capacity and therefore a decrease in the natural processes important for the maintenance of crops.