Depending on the conditions in the weather, the crop and the soil, the question often arises when fertilizing: do I opt for an ammonium or nitrate nitrogen? Practice shows that both forms of nitrogen are needed in the growing season. Nitrate is immediately available and ammonium can be absorbed after nitrification. With a combination of the right fertilizer and organic fertilizer, the nitrogen requirement is covered in the short and long term.
Plants mainly absorb nitrogen in the form of nitrate. This nitrogen form moves with the soil moisture to the roots of the plant. Nitrogen in the form of ammonium is bound to the clay-humus complex in the soil and is therefore virtually immobile. The root must then grow towards the nitrogen.
Nitrate in the soil
The nitrate in the fertilizers ensures smooth growth at the beginning of the season. Fertilizers, such as CAN, contain 50% nitrate nitrogen and 50% ammonium. Application during the growing season immediately provides sufficient nitrate nitrogen in the soil, which means that the growth can be used optimally.
Since nitrate can leach out, nitrification inhibitors are sometimes also advised. These slow down the conversion of ammonium nitrogen. However, this can also hinder the growth of the plant. In addition, with normal application just before the start of the crop, you do not earn back the additional cost.
An excellent alternative to fertilizers with nitrification inhibitors is a blend of CAN, ammonium sulphate and coated urea (for example OCI Exactote† The nutrients in Nutramon KAS en Granular 3 AS are immediately available for uptake by the crop. The nitrogen in the coated urea is released in 2 to 3 months, depending on the temperature. This therefore fits in with the nutritional needs of the crop.
Conversion of ammonium
Only ammonium nitrogen is present in the manure. This is gradually converted into a nitrate nitrogen (see the table below). The conversion of the ammonium into nitrate is also highly dependent on the soil temperature.
| Soil temperature | Time to convert 50% ammonium into nitrate |
| 5 degrees Celsius | 6 weeks |
| 8 degrees Celsius | 4 weeks |
| 10 degrees Celsius | 2 weeks |
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