N-inhibitors aid in greenhouse gas reduction

Research from the University of Guelph indicates the application of nitrogen inhibitors can help farmers significantly reduce their emissions.

While such products can differ in consistency across various growing conditions, their medium- and long-term impacts can still have a major effect. 

Why it matters: Governments are pushing the reduction of climate change-inducing gases and inhibiting nitrogen moving to the air is one way of doing that. 

Nitrogen in soil can be lost via leaching, volatilization (the transfer of nitrogen as ammonia gas from soil to the atmosphere), and denitrification — the conversion of nitrate to nitrogen gas or nitrous oxide by soil bacteria. 

Agriculture and Agri-Food Canada reports nitrous oxide accounts for approximately half the warming effect of agricultural emissions.

While the conversion of nitrate to greenhouse gasses is a naturally occurring process for any nitrogen in the soil, keeping soil-borne nitrogen stable for a longer time reduces the speed at which the cycle occurs, says Pedro Ferrari MacHado, a researcher involved in the nitrogen inhibitor project and a post-doctoral student at the University of Manitoba. 

The reduction potential of inhibitors is significant. The results of the University of Guelph’s three-year field study in corn found two inhibitors, both commercially available, reduced nitrous oxide emissions by more than 50 per cent.

Nitrification and urease inhibitors also decreased the abundance of ammonia-oxidizing bacteria and denitrifying bacteria by 40 to 56 per cent after nine days. No yield reduction or lasting impact on microbial communities were observed.

Nitrogen cycling activity, as described in the project summary, was affected to a lesser extent. Unmeasured effects of microbial components, environmental factors and the legacy of previous years of treatment might be reasons for more field-scale N2O reduction.

MacHado says the findings indicate there is opportunity to drastically reduce emissions, although not in every field or under every circumstance. 

The study, conducted in 2015-17 by MacHado and his colleagues, highlighted several anomalies. Reductions were seen in 2016 and 2017, but higher rainfall resulted in no reduction observed in 2015. Other studies looking at the impact of nitrogen inhibitors show similarly conflicting results. 

Given this reality, MacHado believes a greater meta-analysis of nitrogen-inhibitor research is required to pinpoint where such products can have the greatest effect. 

Despite the variation in effectiveness based on field and weather conditions, inhibitors do have a positive impact over the medium- and long-term. Focusing on effectiveness across multiple years is necessary. Viewed in this way, MacHado says the use of nitrogen inhibitors could fit well within current climate policy. 

“The important thing is identifying the scenarios where they will really work. … I don’t think it’s a no-brainer. It’s the kind of situation that needs to be evaluated with very comprehensive studies.”