Nitrogen Management: How Nitrogen is Lost and How to Protect It 

For an in-depth discussion on the various nitrogen loss mechanisms and how to reduce them, check out this eKonomics episode of The Dirt Podcast where host Mike Howell, Nutrien, Senior Agronomist and guest Greg Schwab, Owner, Schwab Agronomic Consultants and Principal, Elebar Partners, dive into nitrogen management. 

Here are a some of the key takeaways: 

How is nitrogen lost? 

Nitrogen is lost in one of three ways, either through leaching, volatilization or denitrification.  

Leaching is the movement of nitrate nitrogen beyond the root zone of crops, where it can end up in groundwater or surface water.  

Volatilization occurs when urea is applied to the surface of soil. When urea initially breaks down, it converts to ammonia gas, where it can be lost from the soil surface if it is not incorporated into the ground. As much as 30% of applied nitrogen can be lost via volatilization if soil is not tilled or incorporating rainfall does not occur.  

The final loss mechanism is known as denitrification, where nitrate nitrogen is converted into nitrogen gas and leaves the soil. This typically happens when soil is saturated and there is not enough oxygen in the soil profile. Studies show that 2-5% of the nitrate form of nitrogen in the soil can be lost per day of saturation, depending on soil texture and drainage.  

How can you protect your nitrogen? 

Nobody wants to lose nitrogen. It’s a product you pay for, and N loss can lead to losses in yield, costing you more than just lost inputs. There are a wide variety of products currently on the market to reduce the risk of N loss.  

Products with NBPT are designed to reduce ammonia volatilization from surface-applied urea or UAN.  

Urease inhibitors help prevent leaching and denitrification by slowing the conversion of ammonium to nitrate. By keeping N in the ammonium form, less N will be lost to denitrification or leaching.  

Products containing nitrapyrin have been on the market for nearly 50 years and are commonly used with fall-applied anhydrous ammonia.  

There are also slow- and controlled-release products on the market. These use a polymer coating on a nitrogen fertilizer to slow or control the timing of release instead of attempting to inhibit a loss mechanism directly.  

More recently, biological products have hit the market that aim to increase nitrogen through some form of natural nitrogen fixation, though studies differ in proving their efficacy.