Yield Formation and Stability of Maize Under Monoculture in Response to Biological Amendments, Weather Variability and Cultivar Maturity

Contemporary agriculture faces the challenge of sustaining crop productivity amid increasing climatic pressures and simplified agronomic practices, such as monoculture. A field experiment conducted from 2022 to 2024 aimed to determine the effects of meteorological conditions and biological amendments on grain yield and yield structure in three maturity groups of continuous maize (Zea mays L.; FAO 200, 230 and 260). The split-plot experiment included applications of the biological amendments Neosol, Bactim Gleba and UGmax. Deteriorating agrometeorological conditions over the years studied led to a progressive decline in mean grain yield, reaching the lowest value in 2024 (5.06 Mg ha−1). The cultivar belonging to the FAO 260 maturity group exhibited the highest yield potential. Application of all biological amendments resulted in a significant increase in grain yield and thousand-grain weight compared with the untreated control. The most effective treatment was UGmax which increased mean grain yield by approximately 14% and thousand-grain weight by 19% compared with the control. Path analysis revealed hierarchical relationships among components of ear structure and grain yield. The primary direct effect on yield increase was the number of kernels per ear, with thousand-grain weight also contributing significantly depending on maturity group. In later-maturing cultivars, kernel number per ear played the dominant role, whereas thousand-grain weight was more influential in earlier-maturing ones. The economic analysis demonstrated that all of the applied biological amendments generated a positive net profit, with the highest additional revenue obtained following the application of UGmax (160 USD·ha−1). These results confirm that biostimulant application affected grain yield formation, and reduced yield losses under stress conditions.