Effect of bio-fertilizer on growth, development and nutrient content (leaf and soil) of Stevia rebaudiana Bertoni

The aim of this study was to evaluate the effect of bio-fertilizers on growth and development of plants in pots containing (V) vermicompost and (M) cow manure: (soil amendments) and (S) garden soil separately and in combination. In the first experiment, treatments included S (control), SM (soil + 15%M + 0%V), SMV10 (soil + 15%M + 10%V), and SMV20 (soil + 15%M + 20%V) by dry weight (w/w). In the second experiment, mycorrhizae (Glomus mosseae and Piriformospora indica) were also added to the treatments. Plants and soils were evaluated 90 days after inoculation with fungi. At maturity, plant height and stem diameter, leaf area index (LAI), chlorophylls (a + b) content, root length, fresh and dry weights (aerial parts and root), and mineral nutrient content in plant leaves were measured. The obtained results indicated significant differences between treatments. Among all the treatments, interaction of soil amendments and fungus was significant for all traits. Almost the maximum amount of morphological traits was found in the combined applications of soil amendments and fungi. In particular, the highest weights were obtained in the SMV20 treatment inoculated with G. mosseae. Nutrient analysis of leaves, revealed maximum amounts of N, P and K in SMV10 and SMV20 treatments, and the highest amount of Ca and Mg was obtained in plants treated with SM and inoculated with P. indica in comparison to control plants. Also, the highest amount of phosphorous in the soil was obtained when SMV20 treatment was inoculated with P. indica. It seems that the combination of biofertilizers is the best result for the stevia plant growth.