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A breezy approach

Researchers at Agriculture and Agri-Food Canada’s Greenhouse and Processing Centre at Harrow are using wind tunnels to better understand and prevent nitrogen loss and boost the amount available for crops such as corn and wheat. The study has important implications because nitrogen is an essential but expensive component in the production system for both crops.

Dr. Craig Drury is leading the study and evaluating urease and nitrification inhibitors with the two most common sources of applied nitrogen – urea granules and urea-ammonium nitrate (UAN) in combination with different application methods.

According to Drury, nitrogen fertilizers account for 72 per cent of all fertilizer sales in Canada. Meanwhile, he notes that a further breakdown reveals that one-third of fertilizer sales are urea and UAN accounts for 16 per cent.

The study also takes into account some critical changes that have occurred in farming. “Farm sizes have generally increased and farmers are under more and more time constraints, not only in order to plant in a timely manner but to get the fertilizers in the soil in a timely manner,” he says.

At the same time, the number of sources of nitrogen have decreased, namely the use of anhydrous ammonia application and ammonium nitrate. As a result, granular urea and UAN applications have been rising.

In addition, the study is looking at three methods of applying the nitrogen sources: broadcasting, streaming and injection.

“We wanted to look at these different options and determine if there is a better way of applying the fertilizers or a better combination of application methods and fertilizer sources,” says Drury. “How effective are these strategies at keeping the nitrogen in the soil and, ultimately, making it more efficient and thereby enhancing crop yields.”

The researchers are also studying different products that contain nitrogen stabilizers or inhibitors. An example is the urease inhibitor in Agrotain. Urease is a natural enzyme in the soil that allows the urea to convert to ammonium. The inhibitor gives the urea time to move into the soil to reduce the amount of volatilization loss.

There are fertilizer products that contain both a urease and a nitrification inhibitor to decrease ammonia volatilization and slow down the process of converting ammonium to nitrate in the soil (i.e., nitrification).

“We’re looking at different inhibitors and different application methods to try to reduce the losses of nitrogen from the soil system to ensure that more of it goes into crop production and ultimately into corn or wheat grain,” he says.

The wind tunnels are used as a research tool to measure the amount of ammonia that may leave the soil following the different treatments and application methods. Air samples are captured before they go into the tunnel and after they leave it by using pumps and acid traps. By analyzing those samples and knowing the flow rates of the gas samples and wind speed of the tunnels, the researchers can calculate the amount of ammonia that has been lost.

Wind tunnels have been used for measuring ammonium losses from manure application; however, the study in Ontario marks the first time they’re being used for looking at nitrogen sources and application methods.

“Wind tunnels are a diagnostic tool that provides us with a more accurate estimate of the ammonia volatilization losses rather than just measuring the inorganic N in the soils or back calculating losses using final grain yields,” says Drury.

Noting that they only have results from one year, he is cautious when it comes to explaining the data from 2013. In a scenario faced by many farmers in southwestern Ontario, heavy rains forced the researchers to side-dress the nitrogen fertilizers three weeks later than planned.

“So we, and many of the producers in Essex and Kent counties, were applying nitrogen in hot, humid weather, which is a problem as ammonia losses increase with increasing temperatures,” says Drury. As a result, the ammonia losses were extremely high in some of the treatments.

Broadcast urea application, not surprisingly, suffered the greatest losses. When a urease inhibitor was used with broadcast urea, ammonia volatilization decreased by 64 per cent. Similar results were experienced when streaming UAN and comparing to UAN with a urease inhibitor. The latter reduced volatilization losses by 26 per cent. Also of note, injection reduced the losses by 38 per cent, compared to broadcasting urea.

“We’re looking at very dramatic reductions in loss when we either injected or streamed the nitrogen into the soil or when we added the urease inhibitors with urea or UAN fertilizers,” says Drury.

The study will compare the different treatment combinations over three years. Drury expects the next phase may focus on timing and rates to help farmers fine-tune their fertilizer applications.

In addition to helping farmers save money and improve their efficiency, the outcome of the study has the potential to change nitrogen management practices.

“We would like to reduce any of the environmental losses because we’re wasting very expensive fertilizer, and if we can reduce losses, then we might also be able to recommend the application rates that are also more cost effective,” says Drury. “Embedded into the current application rates are the losses that occur. Therefore, if we’re able to reduce losses, then we can better match the nitrogen fertilizer application rate to the crop demands.”