Improving Nitrogen Use in Field Vegetables: Reducing Losses With Nitrification Inhibitors
When nitrogen is applied at the right time, in the right form, rate, and location, crops absorb more of it — reducing losses and improving both environmental outcomes and farm profitability. In intensive field vegetable production on sandy soils, preventing nitrogen losses is a major challenge. Innovative fertilisers can play an important role.
Fertilising for Fresh, Leafy Vegetables
One key reason for the relatively low nitrogen use efficiency in field vegetables is the stage at which many crops are harvested: while they are still actively growing vegetatively. Leafy crops such as lettuce and spinach, but also leek, brassicas and celery, are harvested for their green, succulent tissues — precisely when the plant still contains large amounts of nitrogen in its leaves and stems.
Leafy crops can take up around 15 kg of nitrogen per hectare per day. Their relatively shallow root systems cannot reach nitrogen that has moved into deeper soil layers. The challenge is therefore to keep sufficient nitrogen available in the root zone throughout the growing season, without it leaching away.
Nitrogen in the soil exists in different forms: organically bound nitrogen, ammonium (NH₄⁺) and nitrate (NO₃⁻). Soil organisms mineralise organic nitrogen into ammonium, after which nitrification rapidly converts it into nitrate. Ammonium binds to clay and organic matter and hardly leaches. Nitrate, however, is highly mobile and can easily wash down into deeper layers after rainfall — out of reach of crop roots.
During the growing season, when soil temperature and moisture increase, ammonium converts quickly into nitrate. The risk of leaching rises especially when this conversion happens faster than the crop can take up nitrogen. A practical and effective way to reduce leaching losses is the use of a nitrification inhibitor.
How Does a Nitrification Inhibitor Work?
A nitrification inhibitor slows down the conversion of ammonium to nitrate. This keeps nitrogen in the ammonium form for longer. Ammonium binds to the clay–humus complex (CEC), making it far less prone to leaching.
Under wet conditions, nitrate can also be converted into nitrous oxide (N₂O) through denitrification — leading to nitrogen losses to the atmosphere. By delaying nitrate formation, this risk is also reduced.
Depending on soil temperature and moisture, the effect of a nitrification inhibitor lasts 4 to 10 weeks. Under cooler or drier conditions, it can last even longer. This gives the crop more time to take up nitrogen and increases nitrogen use efficiency.
Nitrogen-Rich Crop Residues
Effective nitrogen management in vegetables includes three key elements:
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ensuring sufficient nitrogen supply during growth,
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promoting strong root development, and
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managing nitrogen-rich crop residues after harvest.
Vegetable crops leave behind nitrogen-rich leaves and stems. Proper incorporation of these residues is crucial to ensure good decomposition. The mineralised nitrogen can then be captured by a following crop, such as a cover crop. While this requires time and planning, it substantially improves nitrogen retention in the system.
Nutramon Care & Dynamax Care in Sustainable Vegetable Production
The challenge in field vegetable production is to combine high yield and quality with minimal environmental impact. Nitrification inhibitors help stabilise nitrogen in the root zone by keeping it in the less leachable ammonium form. This leads to higher nitrogen use efficiency and better crop uptake.
A key advantage is that the nitrification inhibitor can be incorporated directly into Nutramon Care and Dynamax Care. These fertilisers retain the excellent spreading quality of Nutramon and Dynamax, enabling accurate application at wide working widths.
Together, Nutramon Care and Dynamax Care provide all the ingredients needed for efficient nitrogen management:
- higher nitrogen use efficiency
- lower environmental impact
- stable supply of available nitrogen
- high crop performance and yield