Corn response to biological products and a nitrification inhibitor

Atmospheric nitrogen (N 2 ) is converted into ammonia (NH 3 ), a form that plants can use, through biological nitrogen (N) fixation by various microorganisms and bacterial genera. This study assessed the field performance of three biological N‐fixing products, or biostimulants (BS), including Gluconacetobacter diazotrophicus (BS1), Klebsiella variicola (BS2), Methylobacterium symbioticum (BS3), and nitrapyrin, a nitrification inhibitor (NI). We evaluated corn ( Zea mays L.) grain yield, quality, and N use efficiency. A 3‐year field trial was conducted from 2020 to 2022 and included N fertilization rates (0, 56, 112, 168, and 224 kg N ha −1 ) alongside the application of the three BS and NI at 112 kg N ha −1 . Averaged over 3 years, the BS treatments did not enhance corn yield compared to N applied alone. Yield differences between N‐rates were observed each year, with the highest yield at 224 kg N ha −1 ranging between 11,100 and 11,600 kg ha −1 in 3 years. In 2021, 112 kg N ha −1 + nitrapyrin increased yield from 880 to 1460 kg ha −1 compared to BS treatments, except for BS3. Grain N removal increased with increasing N rates (0–224 kg ha −1 ); however, treatments exhibited results similar to those where only N fertilizer was applied. Partial factor productivity with BS applications improved 31% compared to when urea was applied alone as 224 kg N ha −1 , but this did not translate into significant yield gains. Agronomic efficiency had varying results through the years. These findings indicate that incorporating biological N‐fixing microorganisms and NI into urea N management strategies may not consistently increase grain yield and do not significantly reduce the need for synthetic fertilizers in corn production.