15N-Nitrogen Use Efficiency, Productivity, and Quality of Durum Wheat Integrating Nitrogen Management and an Indigenous Bacterial Inoculant in a Single Growing Season

In the Yaqui Valley, Mexico, the current and estimated annual growth rate of durum wheat (Triticum turgidum L. subsp. durum) yield is insufficient to satisfy the food demand that the world will be facing by 2050. Furthermore, besides the high doses of fertilizers applied to wheat in this region, nitrogen-use efficiency (NUE) remains low (<34.4%). A sustainable strategy to reduce the use of fertilizers and to increase crop yield and quality is the use of native plant growth-promoting bacteria as microbial inoculants. This study was performed under field conditions during one agricultural season in the Yaqui Valley, Mexico. It aimed to quantify the impact of the inoculation of a native bacterial consortium (BC) composed of Bacillus cabrialesii subsp. cabrialesii TE3T, Priestia megaterium TRQ8, and Bacillus paralicheniformis TRQ65 on grain yield, grain quality, and NUE (measured through 15N-isotopic techniques) at different stages of development of durum wheat variety CIRNO C2008 under three doses of urea (0, 120, and 240 kg N ha−1) fractionated at 30%, 60%, and 10%. Results showed that yield, quality, and NUE were highly affected by the N doses, while the inoculation of the BC had a lower impact on these parameters. Nevertheless, the inoculation of the BC on wheat had positive effects at the early stages of growth, on plant height (+1.6 cm), root depth (+11.9 cm), and spikes per square meter (+25 spikes m−2). Moreover, the addition of the BC improved N acquisition by the plants, at different crop growth stages, compared to uninoculated treatments. Finally, our results indicated that reducing the N dose from 240 kg of N ha−1 to 120 kg of N ha−1 improved the NUE (27.5% vs. 44.3%, respectively) of the crop. Hence, results of this preliminary study showed that the incorporation of bacterial inoculants into the wheat crop requires a simultaneous adequate N management, in order to obtain the desired positive effect on wheat productivity.