Compost and biochar application mitigates salt stress on barley: monitoring of agronomic, physiological, biochemical and molecular parameters

Background and aimsSalinity is a global issue that adversely affects crop yield and soil fertility. This study aimed to evaluate the impact of compost and biochar on mitigating salt stress in barley.MethodsBarley (Hordeum vulgare L.) seeds were grown under controlled conditions with additions of amendments separately or combined. When plants were 45 days old, salt stress was applied for 16 days and then the different parameters were studied.ResultsThe use of amendments enhanced plant growth under salinity stress, increasing RWC and chlorophyll levels while reducing electrolyte leakage. In general, the addition of compost or biochar separately increased the concentrations of osmoprotectants and the enzymatic activities of SOD and CAT, while significantly decreasing the concentration of H2O2. Conversely, the combined addition of compost and biochar significantly reduced the concentrations of osmoprotectants, the enzymatic activities of CAT and APX as well as the levels of H2O2. At the molecular level, the compost and biochar significantly upregulate stress-responsive genes (such as HvDREB, HvHSP, HvP5CS and HvPIP genes), while their combination moderates gene expression, suggesting a balanced and effective regulation of stress response pathways.ConclusionAdding compost or biochar alone offers optimal protection against saltinity. In contrast, the combination of amendments appears to mitigate the effects of salinity, thereby reducing the need for the plant to develop a strong stress response and express high levels of stress response genes to combat oxidative stress. These results underscore the complementary roles of compost and biochar in enhancing plant resilience in arid and semi-arid environments.