Use of plant growth-promoting rhizobacteria (PGPR) and organic fertilization for soilless cultivation of basil

Today there is a greater environmental and ecological awareness and it is growing the number of farmers who want to adopt sustainable and efficient cultivation systems even if not officially certified as organic. Sustainable and modern cultivation systems must involve organic fertilization and cannot ignore the role of rhizosphere microorganisms. Starting from this premise, this paper aimed to evaluate the use of plant growth-promoting rhizobacteria (PGPR) and organic liquid fertilizers on soilless cultivation of basil. Genovese basil plants were cultivated in pots filled with a substrate inoculated or not with a commercial biostimulant (TNC BactorrS13) containing growth-promoting rhizobacteria (Bacillus spp.). Plants were fed only with water (control without fertilization) or with nutrient solutions (NS) that provided the same amount of nutrients with five combinations of mineral (M) and organic (O) fertilizers: 100 % M, 75 % M + 25 % O, 50 % M + 50 % O, 25 % M + 75 % O, 100 % O. The inoculum of the substrate with PGPR had no significant effect on basil plant growth but showed to be effective in decreasing the nitrate content of basil leaves. Several plant characteristics (e.g. yield, fresh and dry biomass, leaf number and area, stem diameter, etc.) showed to be negatively affected by the progressive reduction of the percentage of mineral fertilizer in the nutrient solution, in favor of the organic one, which, on the other hand, determined a significant reduction of the nitrate content of basil leaves.