Synergistic Effects of Microbial Inoculant and Biostimulant Seed Treatments on Winter Wheat Yield under Variable Moisture Conditions

Improving the productivity and stability of winter wheat under increasingly variable climatic conditions remains a major challenge for sustainable agriculture. This study evaluated the effects of pre-sowing seed treatment with a microbial preparation (Nando BioExpert) and a biostimulant (Vitazyme), applied individually and in combination, on crop establishment, yield components, and grain yield of winter wheat under unstable moisture conditions in the Right-Bank Forest-Steppe of Ukraine. A three-year field experiment demonstrated that both treatments positively influenced plant growth, while their combined application produced a pronounced synergistic effect. Seed treatment enhanced plant establishment, resulting in a higher plant density at emergence compared to the untreated control. This improvement contributed to increased productive tillering and a moderate rise in thousand-kernel weight. As a result, grain yield was consistently improved across years, with the combined treatment showing the greatest effect. On average, yield increases reached up to 37% relative to the control, indicating improved resilience of winter wheat to environmental stress. The findings suggest that integrating microbial inoculants with biostimulants is an effective agronomic strategy for enhancing winter wheat productivity under moisture-limited conditions, supporting the transition toward more sustainable and resource-efficient crop production systems.