Microbial Biostimulants Improve Germination, Growth and Nutrient Availability of Ornamental Kale in Sustainable Peat‐Free Cultivation
Ruvini Ranasingha, Anya Perera, Kambiz Baghalian, Chungui LuABSTRACT
Introduction
Ornamental kale ( Brassica oleracea var. acephala ‘Frost Byte’) is valued for both ornamental and edible use, but its successful establishment depends on suitable growing substrates. While peat‐based media provide favourable water retention and aeration, environmental concerns over peat extraction have driven interest in peat‐free alternatives, which may have limitations in nutrient buffering and structural stability. Microbial biostimulants containing plant growth‐promoting bacteria (PGPB) offer a potential solution by enhancing nutrient availability, improving substrate conditions and stimulating early root development.
Methods
This study investigated the combined effects of microbial biostimulant application and substrate composition on germination, growth, pigmentation and nutrient dynamics in ornamental kale. A factorial glasshouse experiment compared two peat‐based substrates (JF, VT) and two peat‐free substrates (PF, MP), each with or without the microbial biostimulant Vitalnova TriBoost (0.5 g L −1 ). Plant growth parameters and substrate physicochemical properties were analysed.
Results
Microbial biostimulants improved plant establishment across substrates, although responses were strongly substrate dependent. In peat‐based media (JF, VT), germination showed only minor changes, increasing by 10% in JF while VT remained unchanged, with 7%–17% increases in crown diameter and plant height and up to 25% more leaves. In peat‐free substrates, germination increased by about 13% in PF and 80% in MP, despite more limited gains in vegetative growth. Biostimulant application also enhanced substrate properties, increasing phosphorus by about 50% and potassium by 70%–125% in peat‐based media, while in peat‐free substrates it reduced bulk density by up to 18% and increased phosphorus by 33%–50% and potassium by 90%–95% indicating improved nutrient availability and structural conditions.
Conclusion
Overall, microbial biostimulants can enhance the performance of peat‐free growing media, partially mitigating their structural and nutritional limitations, highlighting their potential to support more sustainable peat‐free horticultural production.