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

Abstract

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.

Engineering clay minerals to manage the functions of soils

“…However, with the increase in application rate, the growth index of Pakchoi decreased sharply, which may be related to the rise in soil pH value and salinity. Therefore, Si fertilizer may be a potential choice for improving crop yield ineffective Si-deficient soils under the control of dosage application (Wang et al, 2021). Moreover, many bacterial biologics are synthesized from solid carriers (talc or compost).…”

“…Borges et al (2015) conducted a series of studies on the mechanochemical transformation of clay minerals, converting talc into a slow-release fertilizer using mechanochemical methods. Due to the fact that talc is rich in silicon (its silicon content theoretically can reach 63.3%) and contains almost no toxic heavy metals, it can be inferred that talc has the potential to be used for the preparation of silicon fertilizers (Kalantari et al , 2014; Wang et al , 2021). Pot experiment results showed that a soil Si-talc fertilizer application of 5 g kg –1 was the most effective for the growth of pak choi.…”