Polyhydroxyalkanoate-Based Fertilizers for Phosphorus Slow Release

The exploration and use of biodegradable polymers to develop both environmentally and agronomically efficient slow-release fertilizers are rapidly growing. Polyhydroxyalkanoates (PHAs) are biodegradable polymers produced by microorganisms. Among agricultural soil-treatment solutions, they are mainly used as carrier agents for pesticide and herbicide formulations. In this study, PHA-based orthophosphate (OrthoP) fertilizers were developed using extrusion to enable slow release of P. The pellets were characterized in terms of elemental composition, morphology, specific gravity and bulk density, water vapor sorption, and attrition resistance. The P release kinetics in water was monitored, and the effects of extruded pellets on the germination index and dry biomass of tomato, as well as their disintegration in the soil, were assessed. The results demonstrated mechanical performance enhanced by more than 10% and water half-release times ranging from 0.5 h for the initial pellet to 140 h for the slowest-releasing pellet. These improvements could optimize P fertilizer efficiency under field conditions, aligning with the principles of precision agriculture.