Impacts of early drought stress and plant-based biologicals on malting and feed barley quality

Introduction Extreme weather events associated with climate change, including prolonged drought periods, are becoming increasingly frequent. For many years, pesticides and mineral fertilizers have contributed to stable crop yields; however, their use is expected to be further restricted due to their negative environmental impacts. Therefore, biologicals are considered as environmentally friendly alternatives. This study aimed to investigate the effects of early drought stress on grain quality in spring malting and feed barley ( Hordeum vulgare L.), as well as to examine how biologicals - specifically Cropcover and Giant knotweed - affect these quality traits. Methods Four malting and four feed barley genotypes were evaluated under field conditions at two locations over three consecutive years. All genotypes were tested with and without application of biologicals. Drought stress was imposed from BBCH 13 for six weeks. Mature plants were harvested, and grains were analyzed for grain size, C/N ratio, crude protein content, and starch content. Results Early drought stress significantly (p < 0.05) increased crude protein content in year 2021 and 2022 exceeding the acceptable level of 12% for malting barley, while reducing grain size and C/N ratio, without affecting starch content. Application of Giant knotweed further significantly (p < 0.05) increased crude protein content and decreased the C/N ratio in both malting and feed barley. Discussion These results highlight the pronounced effects of early drought stress and biologicals on barley grain quality, with feed barley quality showing clear benefit.