Nitrogen is one of the most abundant elements in plants as it is a major component of proteins. The amount of nitrogen required by a crop is large compared with the natural nitrogen reserves in most soils, and so mot crops respond positively to additional nitrogen, whether from animal manures or inorganic fertilizers.
Purpose of nitrogen:
Nitrogen is component of vitamins, amino acids and energy systems within the plant, which form its protein. Thus N is directly responsible for increasing protein contain in plants
Causes of deficiency:
Nitrogen is very soluble, so it is easily washed out of soil in rains. Nitrogen deficiencies always affect the oldest, lowest leaves first.
Nitrogen deficiency can easily observe by visual as it is very apparent. Leaves become pale green/ yellow in insufficient nitrogen situation. Some lab test such as soil tests and plant tissue test are taken to have more detail and more accurate data on the nutrient of the plant.
Symptoms of deficiency:
The green pigment in leaves is from chlorophyll. A nitrogen shortage will cause a lack of chlorophyll and leaves become yellow. Sometimes, some leaves might spot with pink tints. In longer period of deficiency of nitrogen, the plant will be become spindly (long, tall, thin) yellow plant.
Flowering, fruiting, protein and starch contents are reduced when supply of nitrogen is in shortage.
Stunted plant growth happened when insufficient nitrogen supplied to the plant. Nitrogen is essential for cell division and enlargement. When it is lacking, plants will be shorter than usual and the leaves may be smaller. Maturity may be delayed too.
In long term, can mulching organic matter (rotted garden compost/ manure) into the plant. Although organic method requires time, it will result in a more even distribution of the added nitrogen over time. In case of boosting nitrogen in the plant in short term, apply high nitrogen fertilizer is always the only way.