Integration of Microbial Biostimulants with Reduced Dose of Phosphate Fertilizers: Effects on Plant Physiology, Growth and Yield of Field-Grown Cucumbers

Application of microbial biostimulants can reduce the need for applying mineral fertilisers, particularly those with limited availability or high environmental impact, like phosphate fertilisers. A consortium of bacterial strains able of solubilizing phosphorous (P) was applied together with reduced P fertilization (60% of standard dose) carried out with either a complex fertilizer (CF) or simple P fertilizer (SF) and compared to standard fertilization rates. Trials with field grown cucumber plants were carried out for four years. The application of the microbial inoculum with reduced dose of both fertilizers did not negatively impact on plant physiological parameters and on yield. The evaluation of the inoculation impact on soil microbial activity, carried out on plants grown in rhizoboxes, showed that the aforementioned inoculation, combined with reduced doses of both fertilizers, significantly increased microbial activity in the rhizosphere compared to fertilizers applied at full doses without inoculation. The results suggest that the integration of microbial biostimulants to a reduced mineral fertilization is a strategy that can be applied also in the long term, leading to a significant reduction in the use of mineral fertilizers and a positive economic and environmental impact.