Vermicompost alleviates the growth, quality, photosynthetic and biochemical traits of Verbena officinalis under salt stress

Soil salinity, an increasing problem both in Turkey and worldwide, negatively affects plants. In this sense, the usage of organic materials is mostly imperative to improve the soil salinity. The purpose of the study was to explore the effects of vermicompost on the growth, quality, photosynthetic and biochemical traits of Verbena officinalis seedlings under salt stress in a greenhouse. Seedlings were applied with or without vermicompost at five different NaCl treatments (0, 20, 40, 50 and 60 mM) in five replicates. Variance analysis showed significant differences among NaCl concentrations with and without vermicompost for all traits. Salt stress caused a decrease in all the studied traits but most in quality traits. Among all traits, the best alleviating effect of vermicompost was found in the growth traits. The means of plant height, plant fresh and dry weights, root length, root fresh and dry weights were 17.8 ± 0.6 cm, 116.8 ± 2.2 g, 5.9 ± 0.1 g, 17.1 ± 0.5 cm, 16.7 ± 0.5 g and 1.4 ± 0.1 g, respectively. Moreover, vermicompost revealed the best increase rate (19–27%) in root traits without salt stress. The current study emphasizes the importance of considering the frequent application of vermicompost, rich in nutrients and microbial activity, to reduce the negative effects of salt and to grow ornamental plants in salinized soils of arid and semi-arid environments. Further research is needed to determine the optimal dosage of vermicompost that yields the greatest positive effects on various traits of V. officinalis , considering different soil conditions with or without salt stress.