Enhanced efficiency fertilizers cut nitrous oxide emissions in spring wheat

Nitrification-inhibitor products – either alone or in combination with an urease inhibitor – reduced N2O emissions by 38% to 43% compared to untreated urea in spring wheat in southern Manitoba. However, there were few yield or grain protein benefits to using the EEFs products.

Environment and Climate Change Canada has set a goal to reduce the amount of greenhouse gas emissions from nitrogen (N) fertilizer by 30% below 2020 levels by 2030. Reducing nitrous oxide N2O emissions will be a key strategy to meeting this goal, while maintaining or increasing crop yields.

A Canadian Prairie research study examined the effect of fall and spring application timings of urea and anhydrous ammonia treated with enhanced efficiency fertilizers (EEFs) on spring wheat performance and N2O emissions. This paper evaluated the impact of using multiple EEF sources compared to conventional urea, and fall and spring application timings, on spring wheat yield and protein content in Manitoba over three years, along with the impact on N2O emissions.

Research was carried out in southern Manitoba at Warren and Glenlea in 2015, Carman and La Salle in 2016, and Kelburn and Ridge in 2017. All sites had residual nitrate-N soil test levels less than 89 lbs./ac. (100 kg/ha), and were on soybean stubble.

Nitrogen fertilizer sources compared were an unfertilized control, untreated urea, and four EEFs including urea plus a urease inhibitor (Limus); polymer-coated urea (environmentally smart nitrogen [ESN]); urea plus a nitrification inhibitor (eNtrench); and a urea plus nitrification and urease inhibitors (SuperU). Application timing included a late fall banding at 1 to 2 inch (2.5 to 5 cm) depth and a spring banding at seeding in a one-pass operation at 1 to 2 inches, both done in a mid-row band placement.

Fertilizer rates were based on provincial soil test recommendations. All plots were seeded to AAC Brandon, and were managed with standard agronomic practices.

Few differences in wheat yield
At 5 of 6 site years, wheat yield and protein content were not affected by N fertilizer source. The only site where N source impacted yield and protein content was Kelburn-17. At this site, the controlled-release product ESN produced significantly higher yield than urea and urea + Limus. It also produced grain protein content significantly higher than urea, SuperU, and urea + Limus.

The impact of application timing on wheat yield and protein content was variable. Three of 6 site-years had lower yield with fall application compared to spring application, while 1 site had higher yield with fall application, and the other 2 sites had similar yields with fall and spring applications. Four of 6 sites had similar protein content for both spring and fall application, while fall application had lower protein content at the other 2 sites.