The influence of algae based biostimulants on growth and flowering of annuals

The production of ornamental annuals is one of the horticultural industry sectors with high mineral fertilization input. At the same time, the awareness of the consumer on environmentally friendly and sustainable production is pushing also the ornamental production toward finding more environmentally friendly solutions. Biostimulants are considered as one solution in reducing the use of mineral fertilizers. The hypothesis was that reducing the mineral fertilization by half and adding algae based biostimulants can improve the growth and flowering of annuals. In this study, the influence of algae based biostimulants on growth and flowering of container grown garden verbena (Verbena × hybrida Lanai ‘Scarlet With Eye’) and calibrachoa hybrid (Calibrachoa × hybrida Cabaret ‘Lavender’) was evaluated. The experiment contained three treatments: 1. Regular mineral fertilization as control; 2. Micro-algae containing biostimulant (Allgrow^®) + mineral fertilizer reduced by half; 3. Seaweed Ecklonia maxima extract and mineral NK fertilizer biostimulant (Basfoliar^® Aktiv, NPK 8-0-18 + microelements) + mineral fertilizer reduced by half. The Allgrow treatment was watered with 2.5% and Basfoliar Aktiv treatment with 0.2% biostimulant solution. The mineral fertilization was through drip irrigation. The rooted cuttings of both cultivars were planted in peat-based substrate into plastic containers. In spring, plants were grown in greenhouse and in summer, in open field conditions in containers. The first watering with biostimulants was two weeks after transplanting. Both biostimulants significantly improved plant growth, flowering and leaf SPAD value of both species compared to control. However, Allgrow’s effect was more significant on all measured parameters compared to Basfoliar. Calibrachoas watered with Allgrow had on average twice as much flowers compared to control.