Nitrogen fertilization: specifics and applications

Nitrogen fertilization is given the greatest attention since it is a nutrient that affects the yield the most. However, if it is incorrectly applied (at an inappropriate time, form or dose), the natural cycle results in its unnecessary loss. This lowers the efficiency of the fertilization, and the costs of the nitrogen fertilizers and their application will not result in the expected yield.

In order to understand the complexity of the use of nitrogen in plant production and its effects on the ecosystem, it is worth recalling nitrogen transformations in soil. The conditions of nitrogen transformation are influenced by soil properties as well as weather patterns. However, it is difficult to predict the weather in the long term, so it is necessary to take into account the current conditions of the year with regard to the fertilized crops, the dose and form of the applied nitrogen. It is therefore generally not possible to prepare a "guaranteed" fertilization method for nitrogen fertilization, but it is possible to build on the knowledge of the transformations described below.

Nitrogen in soil

During the year, there are significant changes in the content of inorganic nitrogen in the soil (chart 1). In spring, from April to May, the warming of the soil increases the activity of microorganisms and the content of mineral nitrogen reaches its maximum values (i.e. spring maximum). In the course of vegetation, the consumption of nitrogen by plants and the gradual reduction in the intensity of mineralization reduces the content of mineral nitrogen in the soil to a relatively stable value just before and after the harvest (summer minimum). Under favourable moisture and temperature conditions, the N-Min content in the soil in autumn begins to increase by the mineralization of post-harvest residues (autumn maximum) and then drops again before winter because microorganism activity decreases due to the drop in temperatures. This great seasonal variability in mineral nitrogen in the soil must be respected and used in practical plant nutrition when determining nitrogen doses for particular crops before planting as well as during fertilization during vegetation.


Mineralization is the process of decomposition of organic matter in soil, during which nutrients that can be used by plants are released from organic bonds. The mineralization of organic nitrogenous substances is generally understood as the process of ammonification, i.e. the conversion of organic compounds to ammonia. In the conditions in the Czech Republic, 50-90 kg N/ha is released in arable soils per vegetation season during mineralization.

Factors affecting mineralization


Under suitable conditions for mineralization, plants have sufficient amounts of mineral nitrogen, often more than with nitrogen fertilizers. Generally speaking, it is also necessary to increase nitrogen fertilizer doses and to use LAV fertilizers in dry weather (as well as in cold weather), and in wet and warm periods it is possible to reduce nitrogen doses, with the exception of very light soils.


Ammonia released by mineralization (ammonification) enters various processes, primarily as the main source of nitrification. Nitrification is a key process in many soils and ecosystems because it transforms a relatively immobile ammonium form into a highly mobile nitrate form of nitrogen. This makes the nitrogen a nutrient that is available to plants, but there is also a risk of its loss by leaching and denitrification.

Factors affecting nitrification


The rate of nitrification is also affected by the type of fertilizer applied. Nitrogen supplied in ammonium form in ammonium sulfate fertilizers is nitrified slowly, but urea nitrogen is nitrified very quickly. After a relatively short period (5-7 days), its nitrification process is similar to that of the transformations of nitrogen supplied in ammonium nitrate (saltpeter) fertilizers (chart 2). Some types of urea-based fertilizers use nitrification inhibitors, but it is important to emphasize that their effects are also greatly influenced by weather patterns.

In warm and dry weather, these inhibitors may paradoxically reduce the availability of N in the urea, especially when it is applied to the surface layers of the arable land, resulting in ammonia losses by volatilization.


Unlike nitrification, denitrification is a reduction process where nitrates are reduced to nitrogen oxides and elemental nitrogen in the presence of readily degradable organic substances. In our conditions, denitrification caused by facultatively anaerobic microorganisms, which use the oxygen from nitrates during decomposition, is prevalent.

Factors affecting denitrification


It is mostly important that there is not high nitrate content in the soils, especially towards the end of the vegetation period and after the vegetation period when there is an increased risk of high water content in the soil and therefore a limited oxygen content. Free nitrates in the soil can be used by a winter crop in the autumn, but if this crop is followed by a spring crop, it is appropriate to use a green fertilizer to reduce the loss of nitrate nitrogen. This also applies to the reduction of the leaching of N outside the growing season. However, nitrate nitrogen is not used by microorganisms during the plant-back of straw because its intake is energy-consuming, so they mostly use ammonium nitrogen instead. Denitrification losses are higher especially when fertilizing with N nitrate in the autumn. The intensity of denitrification increases as the concentration of NO3– increases in the soil; the soil may therefore lose up to 40% of nitrogen from the applied nitrate fertilizers through denitrification.


Volatilization is the process of nitrogen loss from the soil caused by the vaporization of ammonia from the surface or top layers of the soil. Losses through volatilization are about 5 %, but they may even reach over 25 % of the applied nitrogen depending on the soil-climatic conditions, the dose and the form of the fertilizer, as well as the method and time of application

Factors affecting the process


Volatilization occurs after the application of fertilizers containing a large amount of N ammonium (such as liquid manure, slurry, sewage sludge and manure) on the surface of the soil (table). The method and speed of the application of the fertilizer is decisive in this case especially in the first hours after application, as documented in Graph 4. Nitrogen is volatilized similarly during the surface application of mineral N fertilizers that contain ammonia or in which ammonia is formed (e.g. urea).

Key information

The literature used is available from the authors.

Sponsored by the Ministry of Agriculture under Project No. QH 91081


Ing. Jindřich Černý, Ph.D 
Prof. Ing. Václav Vaněk, CSc.
Ing. Ondřej Kozlovský, Ph.D. 

The Czech University of Life Sciences in Prague

Faculty of Agrobiology, Food and Natural Resources
Department of Agroenvironmental Chemistry and Plant Nutrition


SOURCE: ČERNÝ, Jindřich, Václav VANĚK a Ondřej KOZLOVSKÝ. Hnojení dusíkem: specifika a aplikace. Zemědě [online]. 2011, , 1 [cit. 2018-02-12]. Available at: