Field Evaluation of Priestia sp. KR219 in Winter Wheat: Responses Under Different Nitrogen Fertilization Levels

An important component of sustainable agriculture is the development of strategies that reduce the use of mineral fertilizers while maintaining high crop productivity. One promising approach is the application of plant growth-promoting bacteria (PGPB), which may support plant development and improve nutrient use efficiency. A field experiment with winter wheat was conducted in south-western Poland during two growing seasons, 2023–2024 and 2024–2025, to evaluate the effect of inoculation with Priestia sp. KR219 under different nitrogen fertilization regimes. The experiment included three levels of nitrogen: 70, 91, and 130 kg N ha−1 (54%, 70%, and 100% of the full spring nitrogen fertilization rate) with and without bacterial application. Soil chemical and biological properties, photosynthetic pigment content, plant morphological traits, grain yield, as well as grain chemical composition and amino acid profile were evaluated. The inoculated treatments showed higher soil dehydrogenase activity in the second growing season and higher contents of selected photosynthetic pigments, particularly chlorophyll a, under reduced nitrogen fertilization. Bacterial inoculation was also associated with numerical increases in grain yield in most treatment combinations, although these differences were not statistically significant. Differences among treatment combinations involving nitrogen fertilization were more pronounced for grain chemical composition and amino acid profile than differences between inoculated and non-inoculated treatments at the same nitrogen level, with the full nitrogen rate generally resulting in the highest protein content and higher contents of several essential and non-essential amino acids. Overall, the responses observed following Priestia sp. KR219 inoculation included changes in selected soil and physiological parameters, while responses in grain yield and quality varied between growing seasons. Further studies under diverse environmental conditions are required to determine its agronomic potential.