Crop Nutrition

What are the symptoms of Nitrogen deficiency, excess, and toxicity in plants

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20 July 2023, New Delhi: Plants absorb various nutrients to grow. Any imbalance in nutrients may affect the final produce. Hence, a thorough examination of the growing plant can help in identifying particular nutrient stress. Typical signs may show up if a plant is deficient in a specific nutrient. A nutritional deficiency does not immediately result in symptoms. Instead, the regular plant processes are disturbed, leading to an overabundance of some intermediate organic molecules and a deficiency in others. This results in abnormalities that are later recognized as symptoms. 

Symptoms of Nitrogen deficiency, excess, and toxicity in plants


Deficiency of nitrogen causes leaves to turn light green and the older leaves turn yellow. Leaves eventually turn brown and die. Plant growth is slow, plants will be stunted and will mature early.


Plants will be dark green in color and new growth will be succu­lent; susceptible if subjected to disease and insect infestation; and if subjected to drought stress, plants will easily lodge. Blos­som abortion and lack of fruit set will occur.

Ammonium toxicity

Plants fertilized with ammonium-nitrogen (NH4-N) may exhibit ammonium-toxicity symptoms, with carbohydrate depletion and reduced plant growth. Lesions may occur on plant stems, and there may be downward cupping of the leaves and decay of the conductive tissue at the base of the stem with wilting of the plants under moisture stress. Blossom-end rot of fruit will occur and Mg deficiency symptoms may also occur.

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