Lose the loss with nitrogen stabilizers

Does this product work? That’s the question I often get about nitrogen stabilizers. There are plenty out there in the marketplace these days. Pick up any farm magazine (including this one), and you’ll see some type of advertisement or article about nitrogen stabilizer. I know this causes a lot of confusion, so allow me to explain more about their purpose and performance.

Nitrogen stewardship is one of the most important things we can do to protect our yield and environment. Nitrogen stabilizers are commonly used to protect against nitrogen losses through volatilization, denitrification and leaching.

It’s important to understand these processes, so I’m going to get technical. Nitrification occurs when ammonium is converted to nitrite in the soil by nitrosomonas bacteria, and then further oxidized to nitrate by nitrobacter bacteria. A majority of the nitrogen taken up by the plant is in the nitrate form, but most plants can also take up ammonium.

Once in the nitrate form, the nitrogen is subject to loss. Nitrate moves freely throughout the soil profile with moisture. In coarse-textured, well-drained soils, nitrate can leach below the root zone and become unavailable to the crop. Nitrate is also subject to denitrification, a biological process that converts nitrate to a gas that is lost to the atmosphere. This occurs in waterlogged soils.

Currently there are two proven nitrification inhibitors on the market: nitrapyrin and dicyandiamide (DCD). Nitrapyrin has been used since the 1960s. It has long been marketed as N-Serve and most recently as Instinct, an encapsulated product for dry and liquid fertilizers. Instinct can also be used in liquid manure. DCD is the nitrification inhibitor in Agrotain Plus and Super U.

Growers often ask me just how long N-Serve protects nitrogen in the soil. A general rule of thumb is 90 days for fall-applied nitrogen. Keep track of those days by counting the date of application until soil temperatures drop below 40 degrees. Resume counting in spring when soil temperatures warm above 40 degrees. In the spring, expect eight weeks of activity from an April 15 nitrogen application, seven weeks from a May 1 application and six weeks from a May 15 application. Research indicates about a 7-percent yield advantage from fall-applied nitrogen and a 5-percent advantage from spring applications.

Another nitrogen loss avenue is volatilization—the loss of free ammonia to the atmosphere. This process has several steps. First, an enzyme (urease) in the soil and organic residue act on urea and convert it to an unstable form, which can quickly change to ammonia and carbon dioxide. With ideal conditions, this unstable form is converted to ammonium and is available for plant take-up.

However, when conditions are less than ideal, the ammonia can be lost into the atmosphere. Factors that influence this process are urease activity, temperature, soil moisture, application method, soil pH and cation exchange capacity, a measure of the soil’s ability to hold positively charged ions.

The greatest potential for loss occurs when there are high amounts of residue on the soil surface and the nitrogen source is applied on top of the field. In MFA’s trade territory, the most common concern I hear from growers is about how much nitrogen they have lost when an application is followed by a week of hot, windy and dry days.

Research shows that the potential for nitrogen losses through ammonia volatilization can be reduced when using a urease inhibitor to slow or delay hydrolysis. Slowing this process gives Mother Nature a chance to provide precipitation that moves urea into the soil. The most effective inhibitor currently available is Agrotain (nBTPT).  

Then the question becomes, “How much nBTPT is getting put on my urea?” A few of the products on the market today state they have nBTPT in the jug.  While that may be true, be sure you find out how many parts per million the product provides on a ton of urea.

Nitrogen loss can be one of the most yield-limiting factors in the field. Keeping nitrogen in the root zone and available for the crop not only provides a return on the investment for the grower but also has a beneficial environmental impact by reducing losses into the water and air. Check with your MFA or AGChoice location for more information on using nitrogen stabilizers this spring.