Release behavior and biodegradability of controlled-release potassium fertilizer encapsulated in starch–alginate matrix

Abstract

This work presents the fabrication of potassium chloride encapsulated in starch–alginate matrix, crosslinked by calcium chloride to form hydrogel bead. Sixteen formulations (S1–S16) were designed in four levels sodium alginate (SA 0.5% w/v to 2.0% w/v) and potassium chloride (KCl 5% w/v to 20% w/v) with 10% w/v starch and 0.75 M calcium chloride. The analysis reviewed that a higher concentration of sodium alginate, coupled with a lower KCl concentration, results in enhanced encapsulation efficiency. Notably, hydrogel beads formulated with higher concentrations of SA exhibited a more uniform, spherical shape with compact surfaces. Higher SA concentration has lower the swelling of the beads and therefore reduces its potassium release in general. In another word, with higher SA concentration, the release rate was at a better control to the expected release timeframe. On the contrary, it was also observed that the sample's dissolution in water after 24 h increased with the rising SA content. A higher concentration of sodium alginate led to an increased biodegradation rate, with the biodegradation rate increasing by 25% as the SA concentration was raised from 0.5% to 2% over a period of 5 days. In conclusion, this study represents a preliminary exploration into the viability of encapsulating potassium within a starch/SA matrix, with the optimal ratio of starch, alginate, and potassium was found to be 10:2:5. The significance of this work lies in its potential applications within agricultural practices, particularly in drought-prone regions, owing to its hydrogel properties. By precisely tailoring the starch, alginate, and potassium ratios, this study opens avenues for further advancements in sustainable nutrient delivery systems.