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  Nitrogen in soil and plants | Symptoms of nitrogen deficiency or increase

Nitrogen in soil and plants | Symptoms of nitrogen deficiency or increase

Nitrogen is a major material for cell reproduction and development of plant organs, as it increases the area of ​​the leaf surface, increases the active apoplasmic mass, and reduces the thickness of cell wall .

Nitrogen in soil

The igneous rocks do not contain nitrogen in a large proportion, but there is equivalent to 95 - 98% of soil nitrogen in the organic form, most of which was fixed from the air by the nodes bacteria on the roots of leguminous plants or Azotobacter bacteria that fix atmospheric nitrogen

Sources of nitrogen in soil

Atmospheric nitrogen is the main source of nitrogen in the non-fertilized soil and it can reach the soil through the following methods:
1- Atmospheric nitrogen combines with oxygen during lightning and forms nitrogen oxides that dissolve in rainwater and transfer to the soil. This amount is estimated annually about 3 to 5 kg / hectare in humid areas and it is less than that in dry climates.
2- Some types of bacteria can fix the atmospheric nitrogen and convert it into forms that the plant can absorb to create new organic materials. Some of these bacteria live on the roots of leguminous plants and are called root nodule bacteria  or root bacteria such as the genus Rhyzobium and others live free in soil such as Azotobacter
3- Some plants can fix the atmospheric nitrogen through their vegetation, such as the sespan and casuarina plants, and the nitrogen fixed by the previous methods returns to the soil after the death of these organisms and their residues decogmpose.
4- Adding mineral and organic fertilizers, which are an important source of nitrogenous soil

Nitrogen in plants 

  • Plants absorb nitrogen in the form of nitrate or ammonium , It can absorb some forms of nitrogen, such as urea and amino acids , Although nitrate is the preferred ionic form for most plants, some plants use ammonium when it is available in the medium, such as the rice crop, and at the same time it causes toxicity to some plants such as potatoes and tomatoes.
  •  we notice that adding ammonia fertilizers to acidic soils causes toxicity, but adding ammonia fertilizers to acidic soils reclaimed with calcareous compounds is a good process because ammonium releases calcium that is adsorbed on soil colloids, and thus the plant benefits from it and reflects positively on the plant. Symptoms of toxicity with ammonium are manifested in the small upper leaves of plants, the leaves are curved down, and the coloration of the growing apex of plants is white or reddish color.

Nitrogen concentration in the plant

Nitrogen is concentrated in the leaves, seeds and grains, and its percentage decreases in the stems and roots. Therefore, its percentage varies according to the  parts of plants and the type of plants. The nitrogen content in the plant ranges on the basis of the dry weight of 1- 4%.
And the protein content of the plant is related to the amount of nitrogen present. When the amount of nitrogen decreases, the protein content of plants decreases as the protein percentage is calculated by multiplying the nitrogen percentage of the plant by 6.25.

Symptoms of nitrogen deficiency

  • Plants show signs of general weakness, so the leaves become straight and stiff, with short petioles, their veins appear clearly, and the color of the young leaves is pale green, showing yellow and red colors as the growth stages progress. 
  • The symptoms of deficiency appear in the first stages on the old leaves and then extend to the whole plant, and these symptoms differ according to the plant.
  • In apples and tomatoes, it appears with the yellowish green color of the cochineal anthocyanin pigment, and in Camel's hay, the tiller growth stops and the root system grows to a large degree that is not commensurate with the shoot system and the rate of flowering of plants decreases. In yellow corn, the leaves edges begin to turn yellow, then the color extends toward the base, and the side ends remain green for some time

Symptoms of excess nitrogen 

  • These symptoms appear in places where fertilizers are concentrated, such as concentrating piles of organic fertilizer in one place, as the leaves appear in a dark green color, the plants are rich in succulents with little fibers, maturation is delayed, and the plants lying down so we notice the lying down phenomenon in camel's hay
  • Increased fertilization of fibrous plants such as flax leads to increased production but the quality decreases .

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