Eco-extracts from soil microalgae and cyanobacteria as sustainable inputs for tomato cropping: assessment of their biostimulant effects and performance under greenhouse conditions

The growing demand in tomato production is translated into increased production using an intensive cultivation model, often correlated with reports of overusing chemical fertilizers. Although satisfying short-term production, overdependency on chemical fertilizers negatively impacts the environment. Microalgae and cyanobacteria-based biostimulants, as nature-based solutions, offer a valuable tool for reducing the dependency on chemical fertilizers while assuring sustainable production schemes. Their efficiency under controlled conditions is not fully explored, and studies evaluating their comprehensive performance in promoting tomato growth, physiology, yield and fruit quality are limited to few strains. This study describes the effects of eco-extracts from soil microalgae and cyanobacteria on tomato agronomic traits promotion under greenhouse conditions. The findings indicated that soil drenching with low dose eco-extracts significantly promoted tomato performance, with no phytoinhibitory effects. Biometric and physiological attributes were enhanced from + 9% to + 165%, as compared to untreated plants. Plant productivity disclosed no significant enhancements, yet fruit fresh weight and caliber were significantly improved. Fruit quality, particularly total soluble sugars and lycopene, displayed the highest improvements, with enhancements exceeding + 100% as compared to untreated fruits. Postharvest soil physicochemical analyses indicated improved organic carbon content, higher nitrogen levels, and decreased available phosphorus concentrations. These effects were postulated to be linked with eco-extracts biochemical composition, especially indole-3-acetic acid, polyphenols, and flavonoids. Multivariate comparisons designated Nostoc punctiforme CY69 among cyanobacteria, and Chlorococcum sp. GA62 among microalgae as the most performing eco-extracts across different tomato traits. The soil application of eco-extracts sustainably improved tomato performance under greenhouse conditions. Inconsistencies among eco-extracts performances were observed, yet applications with Nostoc punctiforme CY69 and Chlorococcum sp. GA62 showcased consistent effects across plant tomato traits. These results primarily highlighted the biostimulant potential of eco-extracts from soil microalgae and cyanobacteria, and their potential formulation as sustainable inputs in tomato cultivation.