Comparing the effect of Frankia nodules and urea fertilizer on biomass and amount of nutrients of alder saplings

Most of the biological nitrogen fixation rate among forest species is related to the symbiosis of Frankia actinomycetes with actinorhizal plants such as Alder. In the present study, we investigated changes in vegetative characteristics, biomass and nutrients of Alnus subcordata  and Alnus glutinosa affected by three treatments including: symbiosis with Frankia nodes (T1), symbiosis with Frankia nodes and fertilization with urea fertilizer equivalent to 50 kg per hectare (T2), symbiosis with Frankia and fertilization with Urea fertilizer equivalent to 100 kg ha (T3) and without symbiosis with Frankia and without fertilizer (control) for 60 days in research greenhouse of faculty of natural sciences of University of Guilan. At the end of the study, the collar diameter and height of the seedlings were measured and biomass of their different parts was calculated by drying in the oven. The percentage of nitrogen, phosphorus and potassium in the components of the plant were also calculated using Kjeldahl, extraction and colorimetric methods, respectively. According to the results of analysis of variance, significant differences were observed between vegetative characteristics, biomass and nutrients of the species under different treatments. Comparison of means with Turkey’s test showed the best performance of 50 kg / ha fertilizer treatment among the treatments. In addition, the performance of Alnus subcordata in the most of cases was better than Alnus glutinosa. The results of the present study indicate the positive effect of nitrogen fertilization on alder seedlings in early stages of growth and in nursery environment and for alder species, 50 kg urea fertilizer per hectare is sufficient. Of course, considering the environmental considerations, the use of nitrogen-containing organic fertilizers is preferable if fertilization is required.