The biological nitrogen fixation (BNF) process in wheat (Triticum aestivum L.) occurs by diazotrophic bacteria, particularly Azospirillum brasilense. However, researches are lacking on BNF efficiency to define how much mineral nitrogen (N) can be applied to achieve more sustainable high yields, and if urea with the urease enzyme inhibitor is less harmful, benefiting BNF in grasses (cereals). Therefore, the objective was to evaluate the effect of N sources (urea and Super N, urea with urease enzyme inhibitor N‐(n‐butyl thiophosphoric triamide) (NBPT) and N rates (0, 50, 100, 150, and 200 kg ha−1) applied in topdressing associated with inoculation with A. brasilense, regarding the leaf N concentration, leaf chlorophyll index (LCI), accumulation of N in the straw and grains, the nitrogen utilization efficiency (NUE), recovery of the applied nitrogen (RAN), physiological efficiency (FE), agronomic efficiency (AE), and wheat grain yield in the Brazilian Cerrado (tropical savanna) region. The N sources provide similar N accumulations in straw and grains, and wheat grain yield. Inoculation with A. brasilense afforded higher N grain concentration (increase in protein content more sustainably) by applying less N fertilizer in topdressing. Inoculation with A. brasilense increased the AE, RAN, and NUE.
Part of the book: Nitrogen in Agriculture