Ectomycorrhiza-hydrogel additive enhanced growth of Norway spruce seedlings in a nutrient-poor peat substrate

Seedling quality is an important input affecting the outplanted seedling performance. Morphological attributes and association with symbiotic ectomycorrhizal (ECM) fungi belong to influential traits determining seedling quality. In this study, the effect of pre-sowing applied commercial additives Ectovit (containing hydrogel and ECM fungi), Mycorrhizaroots (ECM fungi and nutrients) and Vetozen (natural mineral fertilizer) on the growth and ectomycorrhiza formation of Norway spruce seedlings grown in nutrient-poor pure peat in an open nursery site was assessed. Two-year-old bareroot seedlings were transplanted into containers. No significant growth differences were detected between treatments for 1 + 0 seedlings but the values of growth parameters (root collar diameter; stem height; shoot, root and total dry weight) of Ectovit-inoculated seedlings were significantly higher than those in the other treatments including the control after the second (2 + 0 seedlings) and the third growing season (2 + 1). Root-to-shoot dry weight ratio and number of root tips were distinctly higher after the third year compared to the previous two years but they were not significantly different between treatments. Mycorrhizaroots and Vetozen did not have any significant effect on seedling development. Although the occurrence of treatment-specific ECM morphotype was detected in Ectovit-inoculated seedlings, the high total ECM colonization of roots in all treatments including the control indicated a crucial impact of naturally occurring fungi on ectomycorrhiza formation.