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The Ultimate Guide to Nitrogen Fertilizer

Discover the essential guide to nitrogen fertilizer: its importance, types, application, and how to address deficiencies for healthier plants.
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You may have heard, “Add urea to your plants if they are turning yellow.” But have you ever thought about what this phenomenon is and why it happens? Well, let us shed light on this. The yellowing of leaves, if they start from the tip and run down via the middle section, is due to the lack of nitrogen. Note that this is not the only symptom. Your plant may suffer from several growth and developmental issues if the soil surrounding it lacks the required amount of nitrogen when the plant needs it.

So, here is our comprehensive article on nitrogen fertilizers, from their role to their types and sources. We have also explained what can happen to your plant due to a nitrogen deficiency and how to fix it.

What is a Nitrogen Fertilizer?

A nitrogen fertilizer is a natural or synthetic substance added to the soil to support a plant’s growth. Although it is available in many different forms, it works only if the plant gets what it needs.

Why is Nitrogen Important for Plants?

Why is Nitrogen Important for Plants

Due to leaching, denitrification, or volatilization, soil tends to lose nitrogen. The scarcity can lead to several developmental issues in a plant.

Remember, every plant needs the nutrient nitrogen to grow tall and strong. This element is behind the green color of the leaves and also how huge they can grow in size.

Here’s how…

Nitrogen is an essential element in chlorophyll, the green pigment that gives plants their green-colored foliage. It is an element that is also an integral part of amino acids. We know amino acids make proteins, and hence, nitrogen contributes to the physical structure of the plant. So, the more nitrogen, the more healthy the plant is – its stalks, leaves, and flowers.

Types of Nitrogen Fertilizer 

Nitrates: e.g., sodium nitrate ((NaNO3), calcium nitrate [Ca (NO3)2], and potassium nitrate  (KN03).

In these fertilizers, nitrogen is present in the form of NO3. The nitrate ions are highly mobile and are easily lost through leaching. On the positive side, these fertilizers control the soil’s acidity as they are basic. 

Ammoniacal: e.g., anhydrous ammonia (NH4), ammonium sulphate [(NH4)2 S04], and ammonium chloride (NH4Cl)

These nitrogenous fertilizers contain ammonia or ammonium as the source of nitrogen. They dissolve in water quickly and are available immediately. The best part of using ammoniacal fertilizers is that they are not lost to leaching as the ammonium ions attach themselves to the soil’s colloidal complex.  

Ammoniacal and nitrate: e.g., ammonium nitrate (NH4N03), calcium ammonium nitrate (CAN), and ammonium sulfate nitrate [(NH4)2S04 NH4NO3]

Both nitrate and ammonium are present in these forms of fertilizers. Nitrates can be rapidly utilized by plants, while ammonium becomes gradually accessible. 

Amide fertilizer: Urea and calcium cyanide

Amide converts to ammoniacal form and then to nitrate in soil. They dissolve in water easily and are readily available for the plant to use.

How to Apply Nitrogen Fertilizer to the Plants

How to Apply Nitrogen Fertilizer to the Plants

Nitrogen can be applied to the plants in two forms: Liquid and dry.

Dry nitrogen: Also known as pelleted fertilizers, these suit plants that require slower release of nutrients. Since nitrogen from dry nitrogen needs to be broken down, you can monitor how much nitrogen the plants get. This also saves your plants from burning due to overexposure. 

However, these are dry and may never move to the plant roots. This also means all the volatile compounds will get evaporated into the air, polluting it considerably. 

Liquid nitrogen: When nitrogen is applied in liquid form, the plant absorbs it quickly and more effectively, as it is absorbed directly by the soil. The concentration is usually high like this, and a higher concentration is just the right thing to grow a plant really quickly. But do not overdo it.

Drop or spray nitrogen fertilizer near the active roots. Another place is the zone where it is more likely to be taken. This will help ascertain that the nitrogen is readily available to the plants. 

Nitrogen Placement for Maximum Advantage

Where you place nitrogen fertilizer is a deciding factor in its absorption. Generally speaking, plants do not spread their roots in another plant’s root area. Therefore, the fertilizer should be added in a manner that all plants can have access to it. 

The first thing one must consider is the moisture content in the soil. Without sufficient amounts, it would be difficult for the roots to access the fertilizer placed below the soil surface. 

The broadcast and banding methods of applications work best for this. Here’s an example that pertains to corn plants. Urea ammonium nitrate and anhydrous ammonia, when banded in alternate rows, are equally effective as in the middle. This makes it accessible to all the plant rows. 

Note: adding nitrogen and phosphorus together enhances phosphorus uptake. This is especially seen when the soil is alkaline, and nitrogen is in NH₄⁺ form. 

So, how do you learn that your plant needs nitrogen? Keep reading.

Signs of Nitrogen Deficiency in a Plant

If your plant is deficient in nitrogen, here’s how you can spot it:

  • The plant is relatively shorter. 
  • Bigger leaves start turning pale green first and then yellow to finally white. This starts in a v-shape at the tip and moves along the midrib.
  • Smaller leaves and their stems turn red or sometimes purple. For instance, in tomato plants, the underside of the stems and leaves turns purple.
  • Stems develop purple vertical stripes
  • Veins become red
  • The cannabis plant goes into dormancy.
  • Fewer flowers and fruits than usual are borne by the plant.
  • Leaves start curling inside and then fall off.
  • In crops, N deficiency manifests as a necrotic tissue. 
  • Crop yield decreases significantly.
  • The plants experience a sudden burst of forced blossoms.
  • Chlorosis, a condition in which a plant produces less chlorophyll, extends from the bottom to the topmost parts of the plant.
  • Plants experience premature wilting, eventually leading to their death.

So, what causes nitrogen deficiency?

The Main Factors Causing Nutrient Deficiency

The Main Factors Causing Nutrient Deficiency

  • The soil type. Soils such as sandy as well as well-drained soils lose nitrogen to leaching.
  • Soil saturation: nitrogen management when it rains is essential. Heavy downpours or overwatering drains the nutrients out of the soil.
  • Soil moisture: When the water content is low in the soil, the nutrient absorption by plants also stays low.
  • Aeration: The air gaps in the soil enable the delivery of oxygen to nitrogen-fixing bacteria. These microorganisms are responsible for supplying nitrogen to the plants. If the air content is low, the bacteria use nitrite and nitrate, which converts to nitrous oxide, a greenhouse gas.
  • Temperature: nutrients need slightly warmer conditions to dissolve. Microbes, too, become less active in cooler soil. So, cold soil is less conducive to nutrient movement.
  • Higher concentration of micronutrients: When manganese, zinc, and potassium are high in the soil, nitrogen levels are affected.
  • Salinity: high saline activity increases the osmotic pressure in the soil and lowers nitrogen accessibility.
  • Soil acidity: The more acidic the soil, the less nitrogen is available for crops. The pH should be either high or low. 
  • Root health: Only healthy roots can absorb nitrogen. Those affected by pests or other conditions fail to do so. 
  • Infestation by weeds: the presence of weeds initiates nitrogen infestation as they deny plants vital nutrients. 
  • Inadequate fertilization can also cause nitrogen deficiency.
  • Reduced amount of organic matter. The latter is a natural source of nitrogen. When it is low, nitrogen available for plants is naturally low.

How to Fix Nitrogen Deficiency

Both organic and inorganic matter can help fix the issues caused by low levels of nitrogen. 

  • Organic matter: With the help of organic matter, you allow plants to have access to the vital nutrients they need. In addition, it improves moisture content in the soil. You can even make nitrogen fertilizer at home.

Sources: animal manure, green manure, compost, bone meal or blood meal, cocopeat, tree leaves, legumes, nettle slag, edible or non-edible oil cakes, and ashes.  

  • Inorganic matter: Synthetically prepared fertilizers are amendments that help resolve the nutrient deficiency. However, a soil test to determine the amount you need to add to the soil should be carried out before adding these.

Sources: NPK, urea, ammonium nitrate, and nitrolime.

What is the Right Time to Apply Nitrogen Fertilizer?

What is the Right Time to Apply Nitrogen Fertilizer

Fall and spring are the two best times to apply nitrogen fertilizer. In the spring season, add fertilizers before sowing the spring plantations. Similarly, fall application should be carried out before the fall planting. 

Moreover, the right time to fertilize plants is when they need it the most. For instance, wheat imbibes more nitrogen during spring and early summer, whereas corn absorbs more in midsummer. So, the soil must have enough nitrogen during these times. 

Additionally, if no significant nitrogen loss is expected, then supplementing the soil during plantation is sufficient. However, if you know that denitrification can take place, then do not apply the fertilizer at once. Make two rounds of fertilizer application. 

How do You Know it’s Time to Fertilize?

  • Test the availability of nitrogen for the plant. It could be through soil or the plant itself.
  • Consider the amount of moisture in the soil. Even check with the weather forecast to make a more informed decision about the correct time for fertilization.
  • Do not overfertilize in a single go. It is important to follow the recommended rates. Split the applications. Then, adjust the rates based on how much rain falls, taking into consideration the temperature as well.

How to Prevent Nitrogen Deficiency in Plants?

  • Do not dig soil when it is wet.
  • Take a closer look at the weather forecast for the upcoming 7-15 days. This helps in learning about any chances of soil saturation. If yes, then postpone fertilization.
  • Put off fertilization with urea, as this can increase the chances of volatilization.
  • Apply fertilizer only when needed by the crops.
  • Do not fertilize when the temperatures are more than 10°C.
  • If you’re turning a pasture into crops, especially in areas with ample rain or irrigation, minimize the time without crops.
  • Test the soil before planting seeds.

Note: NH₄⁺ makes the soil acidic with its hydrogen ions (H⁺) ions. This acidification can reduce the pH of the soil. This can be controlled by using fertilizers that contain NO₃⁻. However, these are not so commonly used but should be done for better results.

Technology and Nitrogen Fertilization

Technology and Nitrogen Fertilization

Modern technology is making nitrogen fertilization even easier.

Initial dose: There are tools for measuring how much nitrogen dose is needed by your plant at the beginning of winter. These include software or website services that help create fertilization plans and also calculate the dose.

Predictive analysis (for the end of winter): Some basic tools, such as smartphone apps and digital services, help check the amount of fertilizer that is needed at the end of winter. Such tools prove useful in recalculating the nitrogen needed by crops such as in the case of rapeseed. This is purely on the basis of measurements taken at the end of the season.

Tools for managing fertilizer (during the season): Sensors (on foot, machines, airborne) and decision support services are used for the purpose. All these tools work to update planned fertilizer amounts by estimating the crop’s nitrogen needs. Some may also create maps for applications, adjust the timing, and produce recommendation maps. The latter are based on indicators such as vegetation.

Traceability tools: These tools help track fertilization activities in the soil. Tools that are generally used include traceability devices and plot management devices.

Latest geo-positioning technologies: For ensuring that the fertilizers are spaced evenly. Some applications may also help in adjusting the fertilization according to the speed at which the tractor is moving. 

Parting Thoughts

Now that you know what nitrogen fertilizer is and what its role is in a plant, pay attention to a few things. Always use the correct type of the N fertilizer. Make sure the rate and method are perfectly suitable for the plant type. Remember, faltering at these can lead to plant damage. Above all, choose a reputable and reliable fertilizer manufacturer to buy NPK fertilizer

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