Biostimulant activity of individual and blended seaweed extracts on the germination and growth of the mung bean

Experimental alkaline and blended seaweed liquid extracts (ASLE and BSLE, respectively) were produced from red seaweeds (Acanthophora spicifera, Gelidium robustum, and Gracilaria parvispora) and brown seaweeds (Macrocystis pyrifera, Sargassum horridum, and Ecklonia arborea). The effects as biostimulants on the germination and growth of the mung bean (Vigna radiata) were investigated. Variable concentrations (0.06, 0.12, 0.25, 0.5, 1, and 2%) of ASLE and BSLE were applied. There was a significant difference between the effects of the varying seaweed liquid extracts on the mung bean. The maximum increment in the germination percent (9%) over the control was obtained using the 0.5% BSLE from M. pyrifera and G. robustum (MPGR) administered of the original extract, as well as using the 2% BSLE from E. arborea and G. robustum. The best biostimulant effect was observed in the mean shoot length, with an increase of 39%, compared to the control using 0.25% ASLE from E. arborea. Additionally, a maximum total average length increase of 27% was obtained using 2% ASLE from E. arborea, and an increase of 25% was obtained with a 0.25% blend composed of E. arborea and G. parvispora. Compared to the control, the maximum dry weight average with an increase of 45% was obtained with a 0.05% BSLE produced from E. arborea and G. parvispora applied. Overall, the blended extracts from the brown E. arborea and the red G. parvispora showed the best biostimulant effect as shown in the increase of length and weight of the mung bean, compared to all other BSLE tested. This result suggests that the biostimulant activity was enhanced when two extracts were blended, compared with the effect of individual seaweed liquid extracts. The application of algal blends as formulations with biostimulant properties for seed coating/soaking is a promising option for a sustainable agriculture which aims to reduce the use of mineral fertilizers and pesticides. However, more research is necessary to elucidate the relationship between the biostimulant activity and the extract chemical composition.