2019 ASHS Annual Conference

Interest in organic strawberry production is increasing among growers in Florida, while more up-to-date research-based information is needed to help address plant nutrient management challenges in organic systems. Many studies have investigated the beneficial effects of application of seaweed extracts on horticultural crops including nutrient uptake and yield enhancement, improved plant growth performance, and tolerance to biotic and abiotic stresses. Although seaweed extract biostimulant has been suggested to play a role in enhancing root growth and plant nutrient uptake in organic farming, little information is available with respect to the use of seaweed extract biostimulants in organic strawberry production systems. In this preliminary study, the impacts of Stimplex^® on Sweet Sensation^® ‘Florida127’ strawberry plant growth and yield performance were assessed during the 2017-2018 season at the University of Florida Plant Science Research and Education Unit in Citra, FL. Stimplex^® containing cytokinin is a commercial liquid seaweed extract biostimulant derived from Ascophyllum nodosum. The field experiment was arranged in a split-split plot design with 4 replications. The combinations of cover crop (sunn hemp or weedy fallow) and compost (no compost, 22.4 t/ha or 44.8 t/ha) treatments were randomized in the whole plots and the fertilization treatments were included in the subplots. The fertilization treatments consisted of preplant fertilizer application at 84.1 kg/ha N, in-season fertigation at 328.7 kg/ha N, a combination of both, and no fertilizer control. Stimplex^® treatments in the sub-subplots included biweekly root application of Stimplex^® at 4.7 L/ha and no Stimplex^® control. Strawberry tray plugs were transplanted in Oct. 2017 and fruit were harvested from Dec. 2017 to Apr. 2018. Results indicated that application of Stimplex^® didn’t significantly enhance aboveground N accumulation based on plant tissue N analysis and aboveground biomass at the end of the strawberry season. Strawberry plant growth parameters including leaf area, crown number and crown diameter were not significantly affected by Stimplex^® during the season. However, Stimplex^® application resulted in significantly higher marketable fruit number and weight than the control in December, January, February, and March. The whole-season marketable fruit yield of the Stimplex^® treatment was also significantly improved compared to the control. There were not significant interaction effects between Stimplex^® and other experimental factors including cover crop, compost, and fertilization. More studies involving different strawberry cultivars over multiple seasons are needed to further assess the beneficial effects of seaweed extract biostimulants in organic strawberry production systems as well as the underlying mechanisms.