In the current experiment, tomato (Solanum lycopersicum cv. Nostymi F1) was cultivated in an open hydroponic system under optimal or stress conditions caused by reducing the supply of nutrient solution by 35–40% and treated with biostimulants to test whether their application can increase crop resilience to combined shortage of nutrients and water. The four different biostimulant treatments were: (i) no biostimulant application, (ii) treatment with the protein-based biostimulants COUPÉ REGENERACIÓN Plus and PROCUAJE RADICULAR provided by EDYPRO, (iii) treatment with a novel biostimulant based on strigolactones, provided by STRIGOLAB and (iv) treatment with MAXICROP, a commercial product consisting of seaweed extracts. Combined stress significantly reduced NO3−, P, and K in the root zone of tomato plants. However, the application of the strigolactone-based biostimulant to stressed plants maintained NO3− in the root zone to similar levels with non-stressed plants during the first and third months of cultivation. The biostimulants did not increase the vegetative plant biomass at 70 and 120 days after transplanting (DAT). The strigolactone-based biostimulant increased early leaf area development (70 DAT) and early fruit production compared to untreated plants but had no effect on total tomato yield (120 DAT). Maxicrop also increased early fruit yield, while Edypro decreased early and total yield compared to the control plants, an effect ascribed to overdosing, as the application rate was that suggested for soil-grown crops, while the plants were cultivated on an inert substrate. Strigolactone-based biostimulant and Maxicrop could be further studied by testing multiple applications during the cropping period.

Layout:Tjaša Vukmanič and Urška Lisec

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