When deciding which nitrogen fertilizer option – urea, stabilized urea, calcium ammonium nitrate, ammonium nitrate, or a urea and ammonium nitrate solution – is the most suitable, many farmers may face a dilemma.
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As explained by Dr. Gabrielė Pšibišauskienė, Head of Agro Agrotechnologies Development at Linas Agro, both urea or stabilized urea, as well as calcium ammonium nitrate, consistently feed plants with nitrogen over a long period – without large deficit spikes. In turn, supplementing crop fertilization with nitrate nitrogen under changing climatic conditions can yield results that exceed expectations.
“Fertilizing with urea makes it easier to achieve the desired nitrogen rates: this allows farmers to save fuel by avoiding additional trips to the fields and also prevents soil compaction. The urease inhibitor in stabilized urea reduces spring losses due to volatilization. This fertilizer is highly soluble, quickly and evenly disperses in moist soil, and urea granules do not clump in bags, remaining free-flowing,” the expert lists the advantages.
According to her, if the air temperature is not higher than +15°C, urea does not need to be incorporated into the soil, as is necessary at higher temperatures. She adds that nitrogen losses in crops can be even lower if stabilized urea is used for fertilization.
G. Pšibišauskienė draws attention to the fact that biuret used in urea – a chemical compound that is a byproduct of urea-based fertilizers – can cause concern. “High biuret concentration is toxic to plants, and more than 3% inhibits crop growth. However, there is no need to worry because granulated urea contains only 1–1.1% biuret. Urea with this amount of biuret does not harm even young plants.
One type of fertilizer may not be enough
Nevertheless, G. Pšibišauskienė emphasizes that using only one fertilizer will not maximally improve grain yield and quality. According to her, to achieve the best result, it is necessary to evaluate the advantages of specific fertilizers and the investments in them.
“It is important to properly combine different fertilizers considering field properties, crop condition, climatic conditions, soil temperature and moisture, precipitation forecasts, and most importantly – the profitability of nitrogen fertilizers for the farm. It is precisely the combination of these factors that can determine how much of the applied nitrogen will turn into productive ears, grains, proteins, and gluten,” states the Linas Agro representative.
She gives an example that fertilizing winter crops – wheat and rapeseed – in early spring can start with urea and finish in summer with quality-enhancing fertilization. Meanwhile, when fertilizing summer crops, urea incorporated into the soil consistently feeds plants throughout their growing season.
In turn, the effectiveness of urea in winter rapeseed crops has been evaluated under real conditions by fertilizing in autumn – before sowing. It is calculated that the urea rate applied to the soil was 100 kg, or 46 units of active substance per hectare. This solution allows winter rapeseed to be supplied with sufficient nitrogen throughout autumn and enables farms to save operational costs by reducing the number of field trips.
However, the agrotechnology expert emphasizes not to limit to urea alone. According to recommendations, winter crops must be additionally fertilized with nitrate nitrogen (ammonium nitrate) – especially when more intensive care is needed after growth spurts.
Scientific research evaluated the effect of nitrogen fertilizers
Choosing the most suitable nitrogen fertilizers for farmers is not an easy task, but the results of scientific research can make it easier.
Applying the experience of farms in Germany and Poland, this year the Lithuanian Research Centre for Agriculture and Forestry’s Institute of Agriculture (LAMMCŽI) conducted studies in experimental fields on urea (ammonium nitrogen), as well as nitrate and ammonium nitrogen combinations. They revealed that by selecting the correct combinations of different nitrogen fertilizer forms, rates, and application times, better results can be achieved than by fertilizing crops with nitrate nitrogen alone. In winter wheat trials, the urea fertilization rate used ranged from 70 units of active substance per hectare to a profitable ratio between nitrate and ammonium nitrogen rates, considering fertilizer prices.
Commenting on the 2026 trial results, Dr. Virmantas Povilaitis, senior researcher at the LAMMCŽI Department of Plant Nutrition and Agroecology, states that when ammonium nitrate, calcium ammonium nitrate (CAN), and urea were used separately for spring fertilization, the dry biomass of plants did not differ significantly and was respectively 1194, 1175, and 1199 grams per square meter.
According to him, when liquid KAS fertilizers were used for the first fertilization, plant biomass was 1004 grams per square meter. “However, the recorded difference is statistically insignificant compared to other fertilizers. Using different fertilization methods and evaluating the number of productive stems per square meter, they are similar: from 613 to 645 units. Thus, these differences did not exceed the threshold of a significant difference.”
The scientist adds that when fertilizing winter wheat with CAN and urea, the average number of grains per ear was 42 units. Meanwhile, fertilizing crops with ammonium nitrate and a urea and ammonium nitrate solution (KAS) resulted in an insignificantly lower average grain number of 39 units.
“The trial results allow us to state that winter wheat absorbs mineral nitrogen fertilizers quite equally effectively regardless of their type, but timely application is important. However, it is necessary to use other agrotechnical measures – plant growth regulators, plant protection products, and also consider hard-to-predict factors – the impact of natural conditions on plant growth and product effectiveness. Nevertheless, the final yield and grain quality results will be clear after harvest,” comments Dr. V. Povilaitis, senior researcher at the LAMMCŽI Department of Plant Nutrition and Agroecology.
G. Pšibišauskienė adds that to better understand the benefits of fertilizing with different nitrogen forms, it is worth relying on research results conducted by scientists from other countries.
In northeastern Poland (climate similar to Lithuania), research conclusions state that fertilizing winter wheat with urea and ammonium nitrate solution, also known as KAS, the liquid nitrate nitrogen form it contains promotes faster nitrogen uptake. Moreover, stabilized urea effectively supplies crops with nitrogen over a long period. Therefore, combining these different fertilizers allows expecting not only a higher but also a better quality winter wheat yield,” states the Linas Agro representative.
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