Given current fertilizer production costs, many folks have been looking for ways to improve nitrogen use efficiencies in our non-legume cropping systems.

There are several non-economic reasons for placing more emphasis on nitrogen management. International programs such as the Kyoto Treaty have recognized nitrogen compounds as greenhouse gases. The Fertilizer Institute (hardly a major player at Kyoto) has formed an Enhanced-Efficiency Fertilizer Task Force. Several governmental conservation programs are providing cost share incentives for improved crop nitrogen management practices.

MFA's agronomy staff has spent this winter promoting ways to improve fertilizer efficiencies. This activity is nothing new. We do it every year regardless of plant food prices. The difference this year is the level of intensity the topic is receiving.

As nitrogen fertilizer prices increase, interest in using specialty products always follows. Some nitrogen enhancement products are legitimate and have a proven long-term track record. Others do not.

When considering using new nitrogen fertilizer products, base that choice on the manufacturer's reputation, credible non-biased research and a trust in your fertilizer supplier.

Before using enhancement products, plan your nitrogen programs using traditional best management practices such as proper nitrogen fertilizer sources, rates, timings and placements. Then decide whether enhancement products can benefit your operation.

Nitrogen enhancement products fall into three primary categories. These are: inhibitors/stabilizers; uncoated, slow release materials; and coated, water-soluble fertilizers.

The inhibitor/stabilizer products are designed to disrupt the conversion of fertilizer nitrogen to forms that can be lost from the soil/crop system. Some of these products are designed to prevent the conversion of low-loss-risk ammonium nitrogen to high-loss-risk nitrate nitrogen. Others prevent the urease enzyme from hydrolyzing urea and releasing volatile nitrogen gases.

The protection from these products can last from a few days to several months, depending upon environmental conditions. Common inhibitor products used in our region include N-Serve (Nitrapyrin), Dicyandiamide (DCD) and Agrotain.

Nitrapyrin and DCD are nitrification inhibitors–agents that slow the microbial activity responsible for the conversion of ammonium to nitrate. Agrotain is a urease inhibitor that delays urea hydrolysis and subsequent volatilization losses.

Do the inhibitors always increase nitrogen use efficiency? Obviously, the answer to this question is no. Not all environmental conditions are conducive to nitrogen losses. Many producers choose to use the inhibitors as insurance against nitrogen loss, since future environmental conditions cannot be predicted.

Research during the 1980s showed inhibitors to increase crop yields between 56 and 64 percent of the time, depending upon application timing. At responsive sites, average corn yield increases of 5.6 to 8.3 percent were observed.

There are several slow release fertilizers currently being marketed. These materials protect nitrogen by delaying fertilizer solubility. They tend to be more complex and insoluble compared to conventional fertilizers such as standard urea. Materials such as urea-formaldehyde, methylene urea and isobutylidene diurea have been used for many years in cash crop and lawn/turf industries. Traditionally, they have been too expensive for most row crop systems. These materials release nitrogen slowly as soil microbial populations and/or slow chemical reactions degrade their relatively complex nitrogen formulations. Typical release time is 8 to 12 weeks.

Other specialty nitrogen fertilizers are the occluded products. These materials are made by combining starches with urea followed by fixing the fused mix onto inert materials such as perlite. The result is a relatively slow release, environmentally benign nitrogen fertilizer material.

So far, the cost of these materials has been too high for most production agriculture situations.

A final group of enhanced nitrogen products includes water-soluble coated fertilizers. These materials are made as standard fertilizers (usually urea) and coated with various protective shells. The coatings either break down slowly or "soften" to allow the water-soluble urea to diffuse through the coating. Sulfur-coated urea was developed several decades ago and has been a standard coated fertilizer source. Polymer coatings have been around since the 1960s. Most sulfur-coated materials are still relatively expensive, but the polymer coating technology is now becoming more affordable.

Should you consider using enhanced nitrogen materials this year? They will add expenses to your already stretched production costs. However, if your management requires applying nitrogen under high-loss conditions, they may provide economic value. For example, if you must use urea-based nitrogen fertilizer materials under high volatility conditions, it would be wise to treat that urea with Agrotain. If you have questions concerning nitrogen enhancement products, please visit your local MFA certified crop adviser.