Why Do Plants Need Nitrogen? Reasons you Should Know

Why Do Plants Need Nitrogen?

Nitrogen: The Mother of Plant Growth: Do you wonder why plants need nitrogen? Or how do plants use nitrogen? Well, Nitrogen is considered the motor of vegetative and generative growth. Through the soil, the plant takes up nitrogen exclusively in mineral form. Mainly as nitrate (NO3-) and usually only in small amounts as ammonium (NH4+). Nitrate uptake is affected by an excess of phosphates and ammonium uptake by excessive calcium, magnesium, and potassium. In the plant, the mineral nitrogen is incorporated into amino acids, the building blocks of proteins, nucleic acids, chlorophyll, and vitamins. If the supply is too high, increased amounts of nitrate can also be found in the shoot, especially in low-light growing seasons. In this article, we will explain why plants need nitrogen to survive and the effect on plants.

Why Do Plants Need Nitrogen?


Why Do Plants Need Nitrogen?


Nitrogen intervenes extensively in the plant’s metabolism and significantly influences its generative, and mainly vegetative, growth. As a building block of chlorophyll, nitrogen is involved in photosynthesis. It is also a component of important plant enzymes and promotes the formation of gibberellins and cytokinin, which are involved in all shoot and root growth processes. In addition, nitrogen is a component of secondary plant substances such as alkaloids and vitamins.

In the event of nitrogen deficiency, photosynthetic performance declines. Small, narrow, pale green leaves develop, with the older leaves showing brightening and reddish-purple leaf spicules. Leaf drops may also occur if the deficiency is severe. Plants are more susceptible to drought stress. Flower buds sprout earlier than leaf buds (white flowering). In addition, the fertilization ability of the ovules is impaired during flowering. Also, flower bud induction and flower bud differentiation suffer under N deficiency, which favors altering. Fruits remain smaller due to a lower leaf-to-fruit ratio and are insufficiently supplied with sugar. Below a certain supply threshold, the taste and formation of the red over color suffer. Fruits can also ripen if the primary color changes too quickly from green to yellow (from less than 30 mg/100 g fresh weight in apples). Last but not least, a persistent nitrogen deficiency inhibits the storage of N reserves in the wood and thus the supply of leaves and flowers in the following spring.

Excess Amount of Nitrogen

If you ask why plants need nitrogen, we must tell you that a lack of nitrogen and an excess of this nutrient have a whole range of negative consequences. For example, it leads to dark blue-green leaves and late or insufficient shoot termination and lignification. In summer, undesirable new shoots are promoted. In addition, there is a risk of more severe infestation with pests and diseases such as aphids, spider mites, scabs, powdery mildew, botrytis, fire blight, pseudomonas, or rod diseases. Other consequences may include excessive fruit set, increased June drop, fruit russeting, and delayed fruit ripening with delayed or insufficient cover and ground color development. The fruits are not infrequently coarse-celled, soft, and tasteless. They show reduced shelf life (firmness) and increased susceptibility to rot.

Proper nitrogen fertilization is based on the requirements of the individual fruit species. The specified N values are required for the respective crop to supply leaves, blossoms, fruits, new shoots, and flower buds sufficiently, as well as to be able to create reserves.

Different Nitrogen Fertilizers to choose from


Different Nitrogen Fertilizers to choose from


Mineral granules: In practice, granules containing nitrate or ammonium nitrate are predominantly used for nitrogen fertilization; on the one hand, in the form of single-nutrient fertilizers and, for reasons of labor economy, frequently also in the form of low-chloride compound fertilizers. The most commonly used N fertilizers are calcium ammonium nitrate (KAS), calcium nitrate, and the classic N-P-K fertilizers.

Tips: Above pH 7.5, it is advisable to use nitrate-containing fertilizers again due to increased ammonia volatilization.

Mineral liquid fertilizers: Liquid fertilizers, such as AHL (ammonium nitrate urea solution), work even faster. AHL is inexpensive, precisely placed via the herbicide sprayer, and applied in exact doses. AHL causes a slight herbicidal contact effect from 60 kg N/ha based on the salt effect, especially on dicotyledonous, wet weeds (no use on strawberries!).

Stabilized N-fertilizers: The combination of ammonium or amide fertilizers with nitrification inhibitors has resulted in stabilized N-fertilizers. These are artificial replicas of calcium cyanamide. The added nitrification inhibitors slow down the conversion of leaching-protected ammonium to leaching-endangering nitrate over a period of several weeks. As with calcium cyanamide, the duration of effect is mainly determined by soil temperatures and application rates per hectare. At temperatures above 8 °C, conversion to nitrate occurs more rapidly. Optimum nitroso inhibition is generally achieved only from 80 kg N/ha (fertilization effect: four to ten weeks), and a partial effect from 40 kg N/ha (fertilization effect: two to five weeks). A few years ago, several ammonium-emphasized straight and compound fertilizer granules with the new nitrification inhibitor DMPP were launched on the market in the form of the Entec series. DMPP is considered to be more plant-tolerant than DCD.

Nitrogen-containing foliar fertilizers: periods of drought, cold and other stress are known to be better overcome with the help of foliar fertilizers. For this reason, N-containing products, in particular, are mixed in with the usual crop protection measures, especially in the spring. Their effectiveness is always limited compared to soil fertilization and should be considered as a supplement. Among the nitrogenous foliar fertilizers (Table 3), urea, which is fast-acting and usually well-tolerated, plays a prominent role. It is taken up quickly by all green plant parts (up to 70 percent in 24 hours) and converted into plant-available ammonium by an enzyme. In this way, urea acts almost twice as fast as foliar fertilizers containing nitrates.

Final Thoughts: Why Do Plants Need Nitrogen? 

Now that you know why plants need nitrogen, we must inform you that only readily soluble products should be used over the leaf. Because of the risk of phytotoxic damage, low-biuret origins (less than 1.2 percent) should be used. This risk is lower with formulated fertilizers, especially those containing amino acids, which is why they are primarily used for soft fruit. Calcium nitrate is used primarily as a calcium-accentuated foliar fertilizer (19 percent CaO).

Learn more about What do plants need to grow?

Frequently Answered Questions 

How does nitrogen help plants grow?

Nitrogen is part of the chlorophyll molecule, an element that makes plants green and creates food.

Does nitrogen slow down plant growth?

Nitrogen is crucial for plants’ growth and health. While a lack of nitrogen may result in a poor plant, too much nitrogen does have the possibility to slow down growth.

What plants need a lot of nitrogen?

Gardening plants, especially vegetables like peppers, sweet corn, tomatoes, cucumbers, squash, and others, need a lot of nitrogen. Read more about How to increase nitrogen in soil?

How do you know if a plant needs nitrogen?

You can tell if a plant needs nitrogen by carefully noticing the growth. If the growth is stunted, leaves turn yellow and small, which means there is a lack of nitrogen.

Do coffee grounds add nitrogen to soil?

Yes. Sprinkling coffee grounds on the plants or the composting soils  help you add nitrogen to the soil.

Elysha Murphy

I'm Elysha Murphy, the creator of Easier Gardening. I am very passionate about gardening, and love sharing everything I learn about them.

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