Factors Influencing the Biodegradability of Agro-biopolymer Based Slow or Controlled Release Fertilizer

Slow- or controlled-release fertilizer (SRF/CRF), as an eco-friendly fertilizer, is a solution to low efficiency, which impacts unsustainable agriculture. SRF/CRF is designed by aligning the availability of nutrients with the plant’s needs, thereby minimizing environmental losses, mainly due to leaching and volatilization. Biopolymers are natural matrices that are advantageous for controlling nutrient release kinetics because of their biodegradability, renewability, abundance, minimal environmental risk, low cost, and superior natural and modified physicochemical properties. Degraded biopolymers produce secondary nutrients that improve soil quality and soil microorganism biomass. However, SRF/CRF designs based on process technology often do not consider sustainability or biodegradability. The biodegradation mechanism of SRF/CRF composites is complex because it involves various biopolymers and their characteristics and interactions with the environment and microbial decomposers. Here, we have identified routes that influence the biodegradation process based on SRF/CRF composite properties, including material composition, crystallinity, additives, surface charge, composite thickness, fertilizer concentration, particle size, hydrophilic-hydrophobic interactions, porosity, and cross-linking. These aspects are related to controlled release mechanisms in which nutrients contribute to the metabolism of microorganisms for growth. We conclude that biopolymer addition is not always positively associated with biodegradation; it may speed up or slow down depending on the SRF/CRF composite physicochemical properties.