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All kinds of soil conditioners have been used to improve soil quality. The application of many traditional soil conditioners was limited by single performance. In this study, a novel multifunctional microspheric soil conditioner was prepared based on Arabic gum, gelatin, chitosan and β-cyclodextrin. Arabic gum and gelatin (AG-GL) microspheric carriers, which could load ferrous sulfate (FS), were synthesized via complex coagulation method. The AG-GL(FS) microspheres were covered by chitosan quaternary ammonium salt (CQAS) through single coagulation method. And β-cyclodextrin (β-CD) was used as the outermost shell to improve chemical stability of the soil conditioner by saturated solution method. Finally, the novel multifunctional microspheric soil conditioner AG-GL/CQAS/β-CD-FS was obtained and characterized by Fourier transform infrared spectroscopy, thermogravimetric analyzer, polarizing microscope, scanning electron microscope and particle size analyzer. The novel soil conditioner shows good nutrient slowly-releasing, water retention, heavy metal ions adsorption and antibacterial performances with the particle size of 14–17 μm and high thermal decomposition temperature, which has the potential application in improving soil quality.

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.

Traditional soil conditioners can be used as drugs to regulate elements in soil due to overuse or pollution. There are some negative effects such as low efficiency, hard to degrade and harmful to the environment when they are used. Soil conditioners prepared from sustainable macromolecules can reduce or eliminate these negative effects. In this work, gelatin (GL), chitosan (CS), magnesium ammonium phosphate (MAP) and fulvic acid (FA) were combined and prepared into GL/CS/MAP-FA soil conditioner microspheres with core-shell structure through emulsion crosslinking method. Scanning electron microscopy (SEM) and Fourier infrared spectroscopy (FT-IR) analysis results clarified the surface composition of the microspheres and revealed the good coating performance of GL/CS shell materials. The thermal stability of the microspheres was measured by thermogravimetric analysis (TGA). Water-retention, degradation and crop cultivation showed that these microspheres owned good biocompatibility, which can extend the water-retention time of the soil, settle free heavy metal ions and promote crop growth. The load of fertilizer in the microsphere can effectively prolong the release cycle and improve the utilization rate of fertilizer.