Thermal Preparation and Application of a Novel Silicon Fertilizer Using Talc and Calcium Carbonate as Starting...

The deficiency of available silicon (Si) incurred by year-round agricultural and horticultural practices highlights the significance of Si fertilization for soil replenishment. This study focuses on a novel and economical route for the synthesis of Si fertilizer via the calcination method using talc and calcium carbonate (CaCO₃) as starting materials. The molar ratio of talc to CaCO₃ of 1:2.0, calcination temperature of 1150 °C and calcination time of 120 min were identified as the optimal conditions to maximize the available Si content of the prepared Si fertilizer. X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) characterizations elucidate the principles of the calcination temperature-dependent microstructure evolution of Si fertilizers, and the akermanite Ca₂Mg(Si₂O₇) and merwinite Ca₃Mg(SiO₄)₂ were identified as the primary silicates products. The results of release and solubility experiments suggest the content of available metallic element and slow-release property of the Si fertilizer obtained at the optimum preparation condition (Si-OPC). The surface morphology and properties of Si-OPC were illuminated by the results of scanning electron microscope (SEM), surface area and nitrogen adsorption analysis. The acceleration action of CaCO₃ in the decomposition process of talc was demonstrated by the thermogravimetry-differential scanning calorimetry (TG-DSC) test. The pot experiment corroborates that 5 g kg^-1 soil Si-OPC application sufficed to facilitate the pakchoi growth by providing nutrient elements. This evidence indicates the prepared Si fertilizer as a promising candidate for Si-deficient soil replenishment.