Assessing the potential use of Macrocystis pyrifera extracts as a biostimulant—A review

The increased use of chemical fertilisers is linked to several issues, including land degradation, eutrophication, and environmental pollution. Furthermore, the astronomical cost of these fertilisers necessitates the quest for cheaper, more environmentally friendly, and safe natural phytonutrient sources. The liquid derived from Macrocystis pyrifera (giant kelp) has been used to promote the growth and productivity of numerous crops. The extracts contain a high concentration of ascorbate and phytohormones, including cytokinin, gibberellins, zeatin, fucoidan, and indole-3-acetic acid. It also contains phosphorus, potassium, iron, calcium, copper, zinc, manganese, sodium, tannins, and vitamins. Furthermore, giant kelp extract is a beneficial product that promotes seed germination, plant growth, and deeper root development, as well as increasing crop yield and quality under a variety of conditions. In this study, we narratively reviewed studies on giant kelp extract as a potential biostimulant for increasing crop growth and productivity. Furthermore, we highlighted its potential application in smallholder farming systems to provide phytonutrients, as well as research gaps in existing knowledge about giant kelp extracts. In general, giant kelp extract is an environmentally benign and natural biostimulant that can be used to increase the development and production of a variety of crops. Despite the potential of giant kelp extracts, further research is needed on available phytohormones, nutrients, and potentially cheaper preservative extraction methods, as well as the effect of their application on soil properties.