Biostimulant effects of Spirulina platensis and Azolla pinnata on growth, flowering, and quality of Polianthes tuberose L. under NFT hydroponics

Abstract Tuberose ( Polianthes tuberosa L.) production faces increasing constraints from soil degradation, inefficient fertilizer use, and rising production costs, while sustainable nutrient management strategies for soilless floriculture remain insufficiently explored. This study investigated whether partial substitution of mineral fertilization with algal biostimulants could improve productivity and economic efficiency of tuberose under a vertical nutrient film technique hydroponic system. During the 2023 and 2024 growing seasons, mineral nutrition, bio-based extracts of Azolla pinnata and Spirulina platensis , and integrated treatments combining algal extracts with 50% mineral nutrition were evaluated using palm bark as a local substrate. Growth, flowering, postharvest quality, bulb productivity, nutrient status, and economic feasibility were assessed. Significant treatment effects were observed for all major parameters. Integrated nutrient treatments outperformed full mineral nutrition and sole bio-based inputs. Spirulina platensis  + 50% mineral treatment produced the highest stem yield of 94 stems compared with 86 under full mineral nutrition, and achieved the greatest net return of 88.98 USD, the highest return on variable cost of 3.74, and the lowest break-even price of 0.25 USD per stem. While, Azolla pinnata  + 50% mineral treatment ranked second in addition improving productivity and profitability. Although, sole bio-based treatments reduced variable costs, they were less effective in maximizing yield and returns than integrated strategies. These findings demonstrate that partial mineral substitution with algal biostimulants in NFT hydroponics improves nutrient use efficiency, enhances flower production and economic performance, and provides a sustainable strategy for resource-efficient tuberose cultivation.