Nitrogen fertilizers: what they are and how they affect plant growth
It should be remembered that the nutritional needs of plants are quite simple: plants synthesize the substances that are needed for their nourishment starting from simple compounds, present in the air and in the soil.
These substances represent the raw material from which the vegetable processes its food.
Plant tissues are composed of carbohydrates , fats and proteins , whose functioning is coordinated by a large number of enzymes. The plant therefore needs large amounts of carbon, hydrogen and oxygen, which it draws from the carbon dioxide present in the air and water. All the other elements must be supplied by the soil and, some of these, enter the organic substance processed by the plants and form the body of the plant. Unfortunately, nitrogen is not present in the soil in sufficient quantities for the needs of the plants, hence the importance of nitrogen fertilizers.
The effect of the nitrogen supply can be seen from the luxuriant leaf growth and the livelier coloring of the leaves, organs of photosynthesis.
Conversely, nitrogen deficiencies are manifested by a stunted growth of the plant , with the possibility of serious impairments to the reproductive system and various other cellular imbalances, which cause yellowing of the leaves , up to the necrosis of the younger branches.
Excess nitrogen is equally harmful to plants, since even a high luxuriance can be a symptom of imbalance and can lead to less resistance to adversity. With nitrogen fertilizers
The fruits will have a deterioration in quality, with a decrease in the sugar percentage and, instead, an accumulation which is harmful to the feeding of nitric ions, due to the impossibility of metabolizing all the nitrogen.
The excess of nitrates is not only dangerous because it enters the food, but also because these compounds, highly washable, end up in the aquifers, polluting them and altering the ecological balance. Molecular nitrogen (formula N2, the symbol N derives from the Latin Nitrogenium) in its pure state is found in gaseous form, as a biochemical constituent instead, or even as an inorganic compound, in order to be used it must be linked to other molecules which happens in nitrogen fertilizers.
The form that most plants can appreciate best is nitric, but some species, such as oats, rice and corn, respond well to ammonia. Leguminous plants, on the other hand, are able to use some bacteria (Rhizobium) with which they have a symbiotic exchange from which, in exchange for energy and few nutrients, they get directly usable organic nitrogen.
In addition to the ammonia and nitric form, nitrogen fertilizers can be supplied as urea and organic nitrogen. Nitric nitrogen (NO 3-) is the most easily assimilated but also more easily subject to washout. For this reason it is administered in moderate doses and possibly divided over time, in the emergency or emergency phase and, especially on dry ground.
It is marketed as Sodium nitrate or Calcium nitrate, more suitable for calcium-deficient soils. The ammoniacal nitrogen (NH4 +) has a medium release (45-50 days) and thanks to the small size of the colloid, it is subtracted from washout. It is used as a cover, or post-sowing when the plant has sprouted but has not yet fruited.
These nitrogen fertilizers are found in the form of Ammoniaca anidra, Ammonium sulfate, Ammonium nitrate and Ammonium sulfate nitrate, each with different values depending on the type of soil. Urea nitrogen is very slow-release and is used for basic fertilization, it is the closest to the organic form which is the one obtained from the decomposition of biological substances present in the soil. Extremely soluble in water, only as a result of the complete hydrolysis of the colloid, the nitrogen is distributed evenly in the soil where it does not leave acid residues.