Layered Double Hydroxides: New Technology in Phosphate Fertilizers Based on Nanostructured Materials

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.