Preparation and properties of soil conditioner microspheres based on self-assembled potassium alginate and chitosan

Fulvic acid (FA), as one type of soil conditioner, can enhance drought tolerance, improve nutrient ingestion, stabilize pH values of soil, and reduce fertilizer extracting behaviors. Moreover, it shows a good effect on increasing the permissiveness of plants to various environments, and the stress of salinity and drought is included. Therefore, it can be used as an ideal soil conditioner. In order to extend its effect, it may be loaded into the core-shell polymer microspheres. In this study, FA was added to calcium carbonate (CaCO₃) microspheres, potassium alginate (PAL) and chitosan (CS) were assembled outside. Thus, PAL/CS/FA-CaCO₃ microspheres were prepared using layer-by-layer self-assembly methods. The surface morphology, encapsulation efficiency and in vitro drug release characteristics were investigated. It was revealed that PAL/CS/FA-CaCO₃ microspheres were formed with a particle size distribution between 2 and 6 μm due to self-assembly between PAL and CS. Drug release behavior analysis exhibited the sustained release processes were delayed to varying degrees due to different degradation degrees of CaCO₃ microspheres at different pH values. Results also illustrated that these microspheres had a high loading capacity for FA, and possessed good biodegradability. Thus, PAL/CS/FA-CaCO₃ microspheres exhibited promise for future applications compared with that of traditional soil conditioners.