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Nitrogen (N) is a major nutrient used by crops and is most often in short supply. Nitrogen in soil can be found in many different forms. Nitrate N and Ammonium N are the most common forms of inorganic Nitrogen. Nitrate N (NO3-) is readily soluble in water and is therefore subject to loss via leaching and erosion through water transport. Ammonium N (NH4+-NH3), while volatile and can be lost easily through the atmosphere, is also held tightly by clay and soil organic matter.

Two major processes affecting the availability and amount of Nitrate in soil are nitrification and denitrification. Factors influencing whether nitrification or denitrification occur include soil acidity, soil aeration, moisture and temperature of soil, and nitrate and carbon availability. Nitrification results in the mineralization of N, converting organic N into a useable, inorganic form of N such as NO3-. Denitrification results in the reduction of NO3- to a gaseous form of N which is lost to the atmosphere.

As you prepare for Nitrate applications to your crops, you may be faced with choices of which type of Nitrate product to apply. Nitrogen fertilizer products are available in 3 forms: gas, liquid, and solid. Gaseous forms of Nitrate include anhydrous ammonia (82% N) and the conversion process from the gas to a useable form by plants is the slowest of the 3 types of fertilizers.

While special care has to be taken when using this type of fertilizer to prevent losses through atmospheric volatilization, Nitrate in this form is rarely lost through leaching and denitrifcation. Liquid forms of Nitrate include a combination of urea and ammonium nitrate and range from 32% to 38% Nitrate. Using a liquid form of Nitrate such as these is prone to leaching losses and denitrification if the soil is wet or compacted. The urea component is subject to volatilization if surface applied and not incorporated immediately.

The benefit to using this type of Nitrate for plant needs is that the product has Nitrate in a form that is readily available for plants. Solid forms of Nitrate include urea (granular) ranging in Nitrate content from 45-46%. Urea use is common for broadcast applications, but requires plowing under to prevent losses through volatilization. Products are available to be added to Nitrate to prevent losses through volatilization. They are known as Nitrate stabilizers and they might be able to buy you a little more time for Nitrate availability during the spring and early summer. Spring nitrate-N testing may indicate a need for additional nitrogen top-up, or confirm levels are adequate for the particular crop.

Contact SGS for more all of your soil testing needs and for more information on our nutrient testing packages.

Neil Stoller
Agronomist, CCA/TSP
117 E. Main St.
Toulon, IL 61483
t: (309) 286 2761
f: (309) 286 6251
Website: www.sgs.com/us-soil