Microbial biofertilizers and algae‐based biostimulant affect fruit yield characteristics of organic processing tomato

Abstract BACKGROUND Microbial biofertilizers and algae‐based biostimulants have been recognized for supporting sustainable agriculture. Field experiments were conducted in 2022 and 2023 growing seasons in an organic farm located in Ferrara (Italy) with the aim of evaluating plant growth‐promoting microorganisms (PGPMs) and algae‐based biostimulants (Biost) in tomato (Solanum lycopersicum L. ). The experimental treatments were: (i) two microbial biofertilizers (PGPM₁, PGPM₂) and no inoculated plants (NoPGPM) ; and (ii) two algae‐based biostimulant rates (0. 5% (Biost₀. 5%), 1. 0% (Biost₁. 0%) ) and no application (NoBiost). PGPMs were applied at transplanting, while biostimulants at 15 and 30 days after transplanting. Treatments were replicated three times according to a split‐plot experimental design. Plant characteristics were evaluated at 30 days after transplanting in NoBiost treatments. During tomato cultivation, soil plant analysis development (SPAD), nitrogen difference vegetation index (NDVI), leaf area index (LAI) and photosynthetic photon flux density (PPFD) were monitored. Tomato yield was determined. RESULTS PGPM₂ showed the highest shoot biomass (132. 9 g plant −1), plant height (44. 7 cm), leaf number (34. 0 plant −1) and root biomass (9. 22 g plant −1). Intermediate values were observed in PGPM₁, while all parameters were lower in NoPGPM. Both PGPMs achieved higher values of SPAD, NDVI, PPFD and LAI than NoPGPM. Biost₁. 0% increased all measured growth parameters followed by Biost₀. 5% and NoBiost, respectively. Tomato yield was the highest for PGPM₂–Biost₁. 0% (67. 2 t ha −1). PGPMs affected fruit size and sugar content, while biostimulants were associated with color and lycopene. CONCLUSION The application of microbial biofertilizers and algae‐based biostimulants could be part of environment‐friendly practice in organic farming. © 2024 The Author (s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.