Layered Double Hydroxide (LDH) intercalated with phosphate ions (LDH-phosphate) was synthesized by ion-exchange method from a precursor containing nitrate ions between the layers. The materials were characterized by X-ray diffraction (XRD), attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR), thermogravimetric analysis coupled to differential scanning calorimetry and mass spectrometry (TGA-DSC-MS), specific surface area (BET), scanning electron microscopy (SEM), and elemental analysis. We hypothesized that LDH-phosphate can be used as a slow release fertilizer and help increase phosphate fertilization efficiency in tropical weathered soils. This new fertilizer technology was tested in a kinetic study of P release and a bioassay with controlled conditions of light, humidity, and temperature using maize ( Zea mays ) as our indicator plant. The bioassay was performed using an adaptation of the Neubauer method, wherein the LDH-phosphate was compared to the commercial triple superphosphate (TSP) fertilizer in two different weathered soils: a sandy soil and a clayey soil. Under the bioassay experimental conditions, LDH-phosphate increased plant productivity (mass of dry matter), height, and the content of phosphorus (P) in the dry matter. In addition, LDH-phosphate promoted an increase in the soil pH value, contributing to decrease the P adsorption capacity of the soil, making it more available to the plants.
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Benício et al. (2016) studied this question.