Alginate/okra gum microcapsules containing fulvic acid for agricultural applications

Fulvic acid is a polyelectrolyte, soluble under all pH conditions, and contains low molecular weight humic substances. Studies have demonstrated that fulvic acid can influence plant physiology, including seed germination, crop quality, root development, and oxygen transport. Its small molecular size and mobile fraction enable easy absorption by plant roots and leaves, making it a valuable agricultural amendment. However, its direct application is limited by rapid degradation and leaching. This study presents an innovative, cost-effective method of encapsulating fulvic acid in alginate and okra gum (OG) microcapsules. The biocompatibility of alginate and the mucoadhesive properties of okra gum ensure controlled release. The encapsulation process was optimized to achieve maximum yield (95.90%) and efficiency (94.55%) while minimizing the mean particle diameter (728.75 μm). The Box-Behnken design method identified optimal parameters: voltage = 15.11 kV, flow rate = 1.50 mL/h, distance = 9 cm, and sodium alginate to okra gum ratio = 1.5. This methodology successfully optimized the electrospray process for fulvic acid-loaded microparticles. For the first time, this study investigated encapsulating fulvic acid using alginate and okra gum, including sustained release studies and its impact on lettuce growth. A greenhouse experiment with lettuce (Lactuca sativa L.) treated with encapsulated fulvic acid (EFA) was conducted. Foliar applications of 0%, 0.1%, 0.2%, and 0.4% (w/v) EFA were applied twice at 15-day intervals. EFA foliar application significantly enhanced lettuce head weight and chemical composition, improving plant health and quality by increasing nutrient levels of N, P, K, Na, Fe, Cu, Mn and Zn.