IMPORTANCE FOR PLANT LIFE

Along with other elements such as carbon, oxygen, and hydrogen, nitrogen is a fundamental component of amino acids, proteins, and chlorophyll. It is essential for cell formation, growth, and photosynthesis. It supports the development of green tissues and directly increases the crop’s protein content and yield quality.

UPTAKE MECHANISMS

Plants take up nitrogen mainly as nitrate (NO3-) dissolved in the soil solution. Organic nitrogen in the soil, ammonia, or urea is converted into nitrate through microbial and physico-chemical processes. When plants absorb water through their roots to compensate for transpiration losses, nitrates are transported to the leaves with this flow. At the leaf level, nitrates are converted into organic forms and redistributed throughout the plant.

INTERACTIONS AND SPECIAL CHARACTERISTICS

Nitrogen is the first limiting factor for plant growth. The only exception is legumes, which can use atmospheric nitrogen directly thanks to bacteria living in root nodules. Nitrogen is required for the formation of proteins, chlorophyll, enzymes, and vitamins in plants. Therefore, it is the main determinant of growth while also influencing quality.

THE NITROGEN CYCLE

Nitrogen in fertilizers occurs in three forms: ammonium, nitrate, and urea. Immediately after application, nitrate (NO3-) and ammonium (NH4+) can be used by the plant, whereas urea must first undergo hydrolysis (conversion to NH4+) before it becomes available.

Because nitrate is fully soluble in water, it is the fastest form taken up by plants. It increases the uptake of cations such as K+, Ca2+, and Mg2+. NH4+ can be taken up directly or converted to NO3- through nitrification.

Denitrification is the reduction of nitrate to NO2-, NO, N2O, and N2. It is carried out by anaerobic bacteria and is low in well-aerated agricultural soils. Since nitrate is mobile, it can be leached with rainfall; therefore, high fertilizer doses should be split into multiple applications.

Microorganisms use NH4+ and NO3- for immobilization. Organic materials with high carbon and low nitrogen increase immobilization. However, this nitrogen is not lost; when microorganisms decompose, it becomes available again through mineralization.

Urea applied to soil, (NH2)2CO, decomposes into NH3 + CO2. NH3 gas can be lost to the atmosphere (volatilization). During the NH3 → NH4 conversion, OH- is released and pH increases. Volatilization is much higher in soils with pH>7.

SENSITIVITY TABLE & SYMPTOMS

Nitrogen is a basic nutrient for plant growth. It is the main source for the production of proteins, chlorophyll, enzymes, and vitamins. Nitrogen deficiency causes smaller plant organs and reduced yield. In cereals, it is a key factor in increasing the protein ratio.

If nitrogen deficiency occurs early (before stem elongation), the yield loss is at its maximum, because nitrogen demand in the plant cycle is highest at this stage.

SYMPTOMS

With nitrogen deficiency, chlorophyll synthesis decreases → leaves turn yellow and older leaves show drying.

EXCESS

Excessive nitrogen fertilization increases lodging risk in the field, raises costs, and creates leaching losses to the environment. For optimum fertilization, monitoring tools such as KÖKTEN GÜBRE are recommended.

REQUIREMENT

Nitrogen requirement varies depending on crop type, variety, and targeted yield. Nitrogen fertilization should be planned at the correct dose by calculating (nitrogen supplied by the soil + crop requirement).

NITROGEN ORIGIN & PRODUCTION PROCESSES

Although ammonia synthesis was discovered in 1909, it gained real importance in agriculture after World War II. Today, the basis of all nitrogen fertilizers is the Haber–Bosch process, in which atmospheric nitrogen is combined with hydrogen and converted into ammonia. This invention played a critical role in the development of modern agriculture.

The main source of hydrogen used in this process is generally methane (natural gas), so production is a highly energy-intensive process.

Ammonium nitrate is produced by the reaction of ammonia and nitric acid and has high solubility in water.
Combining calcium nitrate with ammonia produces Calcium Ammonium Nitrate (CAB).
Urea is produced by combining ammonia and CO₂;
UAN solutions are obtained from a mixture of urea and ammonium nitrate and can be applied in liquid form.

CORE KEY FACTORS

SOIL NITROGEN CONTENT

Mineral nitrogen analysis at the end of winter → the amount of nitrogen available to the crop in spring can be estimated. During the season, decision tools such as KÖKTEN GÜBRE support dose adjustment.

ORGANIC MATTER CONTENT

Most nitrogen is found in organic matter. Organic matter level → the main indicator that determines mineralization potential.

SOIL TEXTURE

Sandy soils → high risk of nitrogen loss through rainfall-driven movement/leaching.

CLIMATE

In regions with high winter precipitation, leaching losses are greater. Both drought and excess water reduce nitrogen availability.

WATER REQUIREMENT

On average, 10–15mm of water is required for fertilizer granules to dissolve. Studies should be carried out so that liquid fertilizers become preferred due to drought and lack of water.

pH

Low pH slows nitrification bacteria → mineralization decreases. High pH increases volatilization, especially when urea is applied. Since urea can be lost before it dissolves, its liquefied form has always been more prominent.