Comparative Effects of Urease and Nitrification Inhibitor Formulations on Soil Nitrogen Dynamics and Wheat Productivity in a Two-Year Field Trial

Efficient nitrogen (N) management is essential for improving nitrogen use efficiency (NUE) while reducing environmental N losses in wheat production. A two-year field experiment (2023–2024) evaluated six urea formulations containing urease (UI), nitrification (NI), or combined inhibitors for their effects on soil nitrogen transformations, fertilizer N retention, and wheat productivity in a Cambic Chernozem under temperate conditions. Six fertilization treatments were compared: conventional urea (U1), urea with one NI (U2), two UIs (U3), one UI (U4), one UI plus one NI (U5), and two UIs plus one NI (U6). U1 produced the greatest early-season nitrate accumulation (153.4 mg kg−1), whereas fertilizers containing NI reduced nitrate formation and prolonged ammonium availability. The combined formulation containing two UIs and one NI (U6) exhibited the highest and most persistent nitrification inhibition (70.3% at stem elongation), indicating effective regulation of soil N transformations. Although fertilizer N retention declined during crop development in all treatments, U6 produced the highest grain yield (6417 kg ha−1), while U2 achieved the highest grain protein concentration (12.64%). Across both growing seasons, inhibitor-containing fertilizers consistently outperformed conventional urea by improving the synchronization between nitrogen release and crop demand. These findings demonstrate that combining urease and nitrification inhibitors enhances nitrogen use efficiency, sustains wheat productivity and grain quality, and represents a promising strategy for more sustainable nitrogen management under temperate agroecosystem conditions.