Tailoring Alginate Encapsulates for Agricultural Biostimulants

Alginate hydrogels have attracted considerable interest as carriers for agricultural biofertilizers due to their ability to protect and retain bioactive compounds. In this study, alginate encapsulates containing tomato green pomace and liquid fractions of fermented Ascophyllum nodosum were produced by ionic gelation and characterized using rheological, osmometric, and swelling analyses. The influence of alginate concentration, biofertilizer type, fermentation duration, and suspending medium on encapsulate behavior was investigated. All formulations exhibited shear-thinning behavior, while the incorporation of powdered tomato pomace and liquid fractions of fermented seaweed promoted stronger structural interactions within the silica fume suspending medium, resulting in higher viscosities than the corresponding unloaded encapsulates. The extended fermentation of A. nodosum further modified the physicochemical properties of the formulations and increased their resistance to flow. Although alginate encapsulates exhibited similar osmotic properties, swelling measurements revealed differences in network density and cross-linking, highlighting the dominant role of hydrogel architecture in determining encapsulate performance. These findings advance current knowledge on alginate-based encapsulation of agricultural biofertilizers and support the rational design of hydrogel carriers with tailored hydration, transport, and mechanical properties for agricultural applications.