Nitrogen inhibitors reduced N2O emissions without permanently changing soil microbial communities

Mica Tosi, Shannon Brown, Pedro Ferrari Machado, Claudia Wagner-Riddle, and Kari Dunfield. 2020. Short-term response of soil N-cycling genes and transcripts to fertilization with nitrification and urease inhibitors, and relationship with field-scale N2O emissions. Soil Biology & Biochemistry, 142, 107703. doi:10.1016/j.soilbio.2019.107703
Study Summary by Tasmia Kabir and Cameron Ogilvie

key messages

• Applying UAN with nitrification and urease inhibitors decreased N₂O emissions by more than 50%,
• Nitrification and urease inhibitors did not have a permanent impact on the nitrogen-cycling microbial community

---

Using fertilizer efficiently is vital for managing agroecosystems sustainably. It makes the most of crop productivity while protecting the environment. As agriculture has intensified, the use of synthetic nitrogen (N) fertilizers has increased. Nitrogen losses via nitrous oxide (N₂O) emissions represent a global concern. A large amount of global N₂O emissions comes from N fertilizers in agriculture.

Microbial communities control the fate of N in soils including N₂O emissions. Intervening in the microbial processes that produce N₂O, such as nitrification, can help reduce emissions from agricultural fields. Applying fertilizer with microbial inhibitors is one way to accomplish this. This study examined the response of soil microbial communities and different N-cycling groups after applying urea ammonium nitrate (UAN) with or without nitrification and urease inhibitors in corn production.

WHAT THEY FOUND

Researchers found that inhibitors reduced N₂O emissions by more than 50%. After 9 days, nitrification and urease inhibitors decreased the abundance of ammonia-oxidizing bacteria and denitrifying bacteria by 40-56%. N-cycling activity – measured using microbial RNA codes known as transcripts – was affected to a lesser extent. But unmeasured effects of microbial components, environmental factors, and legacy of previous years of treatment might be a reason for more field-scale N₂O reduction.

WHY IT MATTERS

This study evaluated, under field conditions, the microbial drivers behind new chemical strategies to reduce greenhouse gas emissions and combat climate change. The study demonstrated that UAN with nitrification and urease inhibitors could reduce N losses while maintaining crop yields. But additionally, inhibitors only had a temporary effect on N-cycling microbes. Because the effects are temporary, there is less concern that these inhibitors will permanently change the microbial community. Chemical inhibitors are a valuable tool we can use to achieve our 2030 emissions reduction targets.

HOW THEY DID IT

The study considered short-term changes of N-cycling genes and transcripts and N₂O emissions from the soil after applying UAN fertilizer with or without nitrification and urease inhibitors. The research consisted of 4 ha corn plots at the Ontario Crops Research Centre in Elora, Ontario, Canada. They also monitored field-scale N₂O emissions using micro-meteorological techniques for three years. The researchers collected soil samples 10 days before and 2,6,9,13, and 16 days after applying fertilizer. They immediately flash-froze samples to keep soil microbial communities “stabilized”. In the lab, they analyzed N-cycling microbial communities using molecular techniques. Then they reported the changes of N-cycling microbial communities.