An Environment-Friendly Fertilizer Prepared by Layer-by-Layer Self-Assembly for pH-Responsive Nutrient Release

Layer-by-layer (LBL) self-assembly based on natural polysaccharides is drawing significant attention in various applications. However, its application in fertilizers is limited. In this study, LBL electrostatic self-assembly technology was employed to prepare an environment-responsive fertilizer with natural polyelectrolyte layers of chitosan and lignosulfonate deposited on polydopamine-coated ammonium zinc phosphate. The morphology of the fertilizer was evaluated by scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. The composition and self-assembly process of the fertilizer were characterized by elemental analysis, Fourier transform infrared spectroscopy, UV-vis absorption spectroscopy, zeta potential analysis, thermal analysis, X-ray photoelectron spectroscopy, and inductively coupled plasma atomic emission spectroscopy. Excellent pH-responsive behavior was observed by the nutrient release results. In an alkaline medium at room temperature, the nutrient release rate can be clearly accelerated compared with that in acidic and neutral media. Moreover, pot experiments showed that the fertilizer can effectively promote plant growth. The pH-responsive environment-friendly fertilizer can control nutrient release and avoid excessive release of nutrients, showing promising applications in modern green and sustainable agriculture and horticulture.