Environmental trade‐offs of nitrogen fertilizer application in wheat production system

Excessive nitrogen (N) fertilization improves crop yields but leads to significant environmental concerns, such as ammonia (NH3) volatilization and nitrate (NO3−) accumulation. These losses reduce nitrogen use efficiency (NUE) and contribute to air and water pollution, threatening the sustainability of intensive cropping systems. Therefore, this study was designed to evaluate how N rates and sources influence NH3 volatilization, wheat (Triticum aestivum L.) yield, NUE, and post-harvest soil NO3− over two growing seasons. Treatments included were no N fertilizer, 75% recommended N as urea, recommended N as urea, 125% recommended N as urea, recommended N as calcium ammonium nitrate (CAN), and an equivalent to recommended N as animal manure. This study revealed that urea-N and CAN-N application significantly enhanced biomass and grain yield in 2022–2023, whereas in 2023−2024, urea-N75 produced the highest grain yield, closely followed by CAN-N treatment. Higher level of urea increased biomass but not grain yield, indicating inefficient partitioning and ultimately reduced agronomic efficiency (AE). Reduced level of urea consistently achieved higher AE, whereas Org-N was limited by slow mineralization. Residual soil analysis showed greater NO3− accumulation under higher urea levels, but not in CAN-N and Org-N. NH3 emissions peaked after each fertilization, with increases in urea levels, while CAN-N and Org-N mitigated NH3 emissions. Incorporating these strategies into nutrient management systems can support climate-smart agriculture and guide policies toward sustainable agriculture.