Effect of fermented fertilizer obtained from biogas systems on germination, seedling development and leaf volatile components of arugula under salt stress

In this study, the effects of liquid anaerobic digested (LAD) (1%, 5%, and 15%) on physiological parameters and volatile components in arugula (Eruca sativa L.) grown under salt stress (0 mM, 75 mM, and 150 mM) were examined. The experiment was conducted three times in three different stages. In the first two stages, arugula seeds were grown in petri dishes (25 seeds each) and in peat+perlite mixed pots (50 seeds each) for seven days after 1 hour of LAD pre-application. In the third stage, arugula seedlings were grown in peat+perlite mixed pots for 60 days by applying LAD directly to the seedling soil without pre-treatment. A group containing peat+perlite+NPK (15% N, 15% P2O5, 15% K2O) was also included for comparison with LAD. The results of the study showed that salinity caused up to 95% inhibition in the germination and growth parameters of seedlings in petri dishes (seven days old). However, LAD was not able to eliminate this inhibition. Similarly, at the end of seven days, the emergence values of arugula seedlings grown in peat+perlite mixed pots decreased in almost all parameters due to the increase in salt level. LAD pre-application was also unable to eliminate the stress-related inhibition. Only pretreatment of 5% LAD at 75 mM significantly attenuated the inhibition effect compared to other pretreatments at the same salt level. In the third stage, arugula seedlings grown in peat+perlite mixed pots for 60 days were examined for shoot length, shoot diameter, number of leaves, shoot fresh weight, shoot dry weight, water content, and leaf area values. Salt-induced inhibition showed significant negative effects in all parameters. However, LAD (1% and 5%) and NPK had very positive effects in all groups, with or without salt stress, at this stage and eliminated salt stress in all parameters except water content. In the volatile component results, the major component in all groups was 4-methylthiobutyl isothiocyanate and contrary to expectations, no significant change was observed due to salt stress or fertilizer applications.