Nitrogen and plants

Nitrogen is abundantly present in the air and in the earth’s crust, it is a fundamental element in agriculture, essential for the growth of the green parts of the plant, in particular the shoots and the leaves. For this reason, if it is missing, yellowing of the leaves occurs or a delay in the growth of the plant is observed.

Among the nutrients that our vegetables need to live, in fact, nitrogen is one of the fundamental elements, together with phosphorus and potassium, they are the “trinity” of macroelements that underlie the needs of crops and that are generally present on all complete fertilizers. It can be brought to the soil not only by fertilizers but also by crop rotation, thanks to the cultivation of legumes, capable of fixing nitrogen in the soil.

Nitrogen is everywhere in the atmosphere in gaseous form, when we talk about the presence, excess or lack of nitrogen in agriculture we only refer to the nitrogen available to plants, which is the nitrogen fixed in soil by microorganisms. Even under conditions of shortage of useful nitrogen, the medium remains rich in gaseous nitrogen.

Contents [Ocultar]

  • nitrogen deficiency

  • excess nitrogen

  • Fertilize with nitrogen

  • Expansion and evaporation of nitrogen

nitrogen deficiency

Nitrogen deficiency hampers plant growth, slowing it down and, in severe cases, stopping it. A visible symptom is the yellowing of the leaves, which quickly turn yellow, starting with the oldest ones. Therefore, for a good harvest, this element must never be missing, it is important to know the needs of the different vegetables, to fertilize well and to make a balanced crop rotation. For example, cucurbits, such as pumpkins and squash, “guzzle up” a lot of nitrogen, as do peppers, tomatoes and eggplant. Other crops like garlic and onions are less greedy, while legumes are able to “scavenge” nitrogen from the air and also leave it in the soil for other plants.

excess nitrogen

If with little nitrogen the plant does not grow when the element is too important, it has an excessive, unbalanced growth towards the foliar part. Under the impulse of nitrogen, plants produce many leaves, using all their resources, but they do not develop roots and produce few fruits. Excess nitrogen is particularly counterproductive for roots, bulbs, tubers and fruiting vegetables.

For this reason it is necessary to be careful not to exaggerate with the contributions of fertilizer. Especially if we have a lot of nitrogen in the soil, some leafy vegetables like spinach can absorb large amounts of it, accumulating harmful nitrates for our body. The problem of nitrate accumulation arises in many chemically grown vegetables, when liquid fertilizers, especially nitrogen, are used to obtain an abundant crop. Therefore, an organic garden in which plant nutrition is well calibrated produces healthier vegetables than those that can be purchased in supermarkets.

feed nitrogen

All major fertilizers contain nitrogen: for example, a good amount is found in compost, manure and worm castings. Therefore, there is no need for specific fertilizers. Among the natural substances of recovery, you can also put coffee grounds in the garden, which contain a good amount of this element and are perfectly compatible with the organic method.

As we have already said, there are plants capable of taking nitrogen from the atmosphere and transferring it to the soil through their root system, where certain bacteria preside over the process. Legumes have this characteristic and are therefore very valuable for enriching the soil of the garden, they become indispensable in crop rotation. In addition to growing legumes in the rotation, nitrogen-fixing plants can be planted in order to obtain nitrogen: this technique, very common in organic farming, is called green manuring. White mustard, for example, is an excellent green manure plant that can be used for this purpose.

Dilution and evaporation of nitrogen

Nitrogen can be easily washed away by rains, so it is not recommended to fertilize soluble nitrogen in the fall, such as that provided by manure and pelleted pollen, even if the soil is not covered, it evaporates in an ammoniacal form, for which is good for mulch in winter.

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