Nitrogen fertilisers: types, physical properties and when to apply them
· Valerii Korolko · 5 min read
What nitrogen fertilisers are and why they matter
What are nitrogen fertilisers? Nitrogen is the basis of proteins, enzymes and chlorophyll. It is thanks to nitrogen that plants produce greenery, grow actively, form stems and leaves, and build up vegetative mass.
The main function of nitrogen is to stimulate growth and photosynthesis. Its presence determines whether the harvest will be strong or remain poor. A nitrogen deficiency slows growth, turns the leaves yellow and sharply reduces yield. An excess is not an option either, as it promotes excessive growth of green mass at the expense of fruiting.
Nitrogen fertilisers are in greatest demand when growing cereals, vegetables, potatoes, greens, maize and forage grasses. They act quickly, so they are often applied in the early stages of plant development.
It should be understood that nitrogen in the soil is easily washed out by precipitation or evaporates into the atmosphere, so regular replenishment of this element is an essential part of modern farming.
Types of nitrogen fertilisers: classification and examples
What nitrogen fertilisers are there?
Depending on the chemical form, nitrogen fertilisers are divided into the following types:
- Ammonium fertilisers: the main form of nitrogen is ammonium (NH₄⁺) (ammonium sulphate (NH₄)₂SO₄.). Suitable for acidic soils, well retained in the soil and washed out slowly. Promotes long-term plant nutrition.
- Nitrate fertilisers: Nitrogen in the form of nitrates (NO₃⁻) is a fast-acting form (calcium nitrate (Ca(NO₃)₂). Ideal for top dressing in open ground and greenhouses. However, the nitrate form is easily washed out by rain.
- Ammonium nitrate fertilisers: Contain both forms, ammonium and nitrate, which provides a balance of fast and long-lasting action (ammonium nitrate (NH₄NO₃)). This is one of the most popular and versatile options for most crops.
- Amide fertilisers: Nitrogen in the form of the amide group (CONH₂) (carbamide, or urea (CO(NH₂)₂)).
One of the most concentrated forms of nitrogen – up to 46%. After application, the amide form gradually converts into the ammonium form, and then into the nitrate form. Carbamide is a slow-acting fertiliser.
Which nitrogen fertilisers are best?
Ammonium nitrate (NH₄NO₃): a versatile fertiliser suitable for almost all crops, providing a quick effect and long-lasting action, and used in both spring and summer. On the downside, it can acidify the soil and requires dry storage.
Carbamide (urea, CO(NH₂)₂) thanks to its nitrogen content of up to 46%, is suitable for foliar feeding (gentle action, does not burn the leaves) and does not affect soil acidity. However, it takes time to start working and can evaporate (lose nitrogen) if applied incorrectly.
Calcium nitrate (Ca(NO₃)₂) – works ideally in greenhouses, on vegetables, berries and fruit, acts quickly and adds calcium to strengthen plant cells. The downsides include a fairly high purchase cost and instability in the soil (it is quickly washed out by rain).
Ammonium sulphate ((NH₄)₂SO₄) – the nitrogen and sulphur in its composition improve the taste characteristics of fruit; it is a good choice for acidic soils and is washed out slowly by rain. On the downside, it contains less nitrogen (~21%) than other fertilisers.
- For universal use – ammonium nitrate.
- For foliar feeding – carbamide.
- For vegetables and greenhouses – calcium nitrate.
- For acidic soils and fruit crops – ammonium sulphate.
Nitrogen fertilisers: physical properties
Nitrogen fertilisers come in different physical forms, which determine their ease of use, solubility and duration of action.
Characteristics of nitrogen fertilisers:
- Colour: from white (carbamide) to grey or yellowish (ammonium sulphate).
- Form: most often granules, crystals or powder. Granulated fertilisers are convenient to apply with machinery.
- Solubility in water: high, especially for nitrate forms. This ensures quick plant nutrition.
Temperature stability:
- Carbamide and ammonium nitrate may cake at increased humidity.
- Ammonium sulphate has good storage stability.
The form affects the speed of action: liquid solutions work instantly, while granules act gradually and stay effective for longer.
When to apply nitrogen fertilisers: tips for effective use
When should nitrogen fertilisers be applied? It depends on the crop, the soil type and the weather conditions. But there are a few general rules:
- In early spring – to kick-start vegetation.
- At the beginning of summer – to support growth.
- In autumn – less often, mainly for winter crops.
Weather conditions play a significant role: for example, applying fertilisers before heavy rain may bring no result because of leaching, at high temperatures there is a risk of "burns" to roots or leaves, and strong winds reduce the effectiveness of foliar feeding.
Let us consider when and why fertilisers should be applied:
- Before sowing – during primary soil cultivation.
- During the growing season – in the phase of active growth.
- Foliar application – when the plant needs quick help (carbamide dissolves in water and is sprayed onto the leaves).
When using fertilisers, it is extremely important to follow the basic rules: carry out a preliminary soil analysis and observe the manufacturer's dosage!
Natural nitrogen fertilisers
If you are an advocate of organic farming, pay attention to natural nitrogen fertilisers. They act more gently and are safe for the environment, but require more patience.
Examples: manure, compost, green manure crops, vermicompost. Their action is slower and their effectiveness is lower in the short term, but in the long term we obtain a visible improvement in the soil.
Agronomists often ask whether it is possible to switch completely to organic farming. In this case, it should be taken into account that in the first year the yield may fall significantly and it will take you a long time to restore the balance. Moreover, without mineral fertilisers it is very difficult to achieve stable results, so we recommend combining them to achieve the best result: apply organic matter in autumn and mineral fertilisers in spring – this is the optimal option, which reduces the load on the soil while still delivering stable harvests.
Benefits and risks of using nitrogen fertilisers
Benefits: thanks to their fast action, we can see results within 2–3 days. By controlling the dosage, we obtain a stable, high-quality harvest.
Drawbacks: when using nitrogen fertilisers, it must be taken into account that they can acidify soils, nitrogen can be washed out after rain, and excessive, uncontrolled use can pose a health hazard.
That is why Prodservis insists on strict adherence to the recommended dosage, combining with potassium and phosphorus fertilisers and carrying out soil analysis beforehand. You can buy Belgian mineral fertilisers from Prayon by contacting our managers in any way convenient for you.
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