Are gaseous nitrogen losses affected by the fertilizer type and rate in maize?

Nitrogen (N) management practices have the potential to reduce nitrous oxide (N₂O) emissions and ammonia (NH₃) volatilization while enhancing maize (Zea mays L.) productivity. However, the specific effect of N rate and source remains unclear. This study aimed to evaluate, during the maize growing season, the effect of both N rate and source on i) gaseous losses through NH₃ volatilization and N₂O emissions and ii) agronomic traits such as grain yield and N uptake (N_upt). Four experiments were conducted in the humid temperate region of Argentina between 2020 and 2022. Treatments consisted of four N rates, between 0 and 200 kg N ha⁻¹ combined with four N sources [urea, urea with urease inhibitor (U_UI), urea with nitrification inhibitor (U_NI), and calcium ammonium nitrate (CAN)]. We observed a significant response to N fertilization on grain yield with increases from 20 % to 64 %. However, no differences between N sources were determined. CAN presented the greatest N_upt, which was up to 27 % higher than urea-based N sources. NH₃ volatilization was the major N loss process with urea exhibiting the highest values. U_UI and CAN significantly reduced NH₃ volatilization in comparison to urea. CAN showed the highest N₂O emissions, losing up to 1.5 % of the applied N. U_NI significantly reduced N₂O emissions by 50 %. Emission factors for both NH₃ and N₂O were consistently lower than the default values suggested by the IPCC guidelines. In conclusion, N sources such as U_UI and U_NI lead to achieve high grain yields with a low environmental impact.