Development and characterization of eco-friendly starch/polyacrylamide/graphene oxide-based slow-release fertilizers for sustainable agriculture

The goal of this study was to develop a low-cost and eco-friendly fertilizer with slow-release properties for sustainable agriculture. This research presents the development of a new slow-release fertilizer (SRF) by dispersing a commercial NPK-based compound in a starch/polyacrylamide/graphene oxide (ST/PAM/GO) matrix. Six different formulations of ST/PAM/GO-NPK SRFs were prepared using a simple mixing-forming-drying technique, varying the NPK loading levels from 10 to 90 wt.%. Characterization tests revealed the influence of several factors on the SRFs'performance, including swelling, mechanical resistance, and the release rate of nitrogen, phosphorus, and potassium nutrients in water. These factors include the composition of the SRFs (NPK/polymer matrix ratio and the presence of graphene oxide nanofiller) and probable interactions between functional groups of each SRF component, which were investigated by FTIR structural analysis. The porosity of the SRFs was studied using SEM analysis. Finally, the release mechanism of the developed SRFs was examined using various mathematical modeling tools. The Korsmeyer-Peppas model was found to describe the release profile of the SRFs, indicating that the release occurs through a swelling-diffusion mechanism dominated by a relaxation phenomenon. This work offers a sustainable approach to fertilizer development by utilizing biodegradable and renewable materials, such as starch and polyacrylamide, combined with graphene oxide to enhance performance. The findings contribute to the polymer community by demonstrating the potential of polymer-based nanocomposites in controlled-release applications, providing a foundation for future research in sustainable agricultural practices.