Layered Double Hydroxide (LDH) intercalated with phosphate ions (LDH-phosphate) was synthesized by ionexchange 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 LDHphosphate 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.

The current research aims to introduce Layered Double Hydroxides (LDH) as nanomaterials to be used in agriculture, with particular reference to its use as storage and slow release matrix of nutrients and agrochemicals for plant growing. Structural characteristics, main properties, synthesis methods and characterization of LDH were covered in this study. Moreover, some literature data have been reported to demonstrate their potential for storage and slow release of nitrate, phosphate, agrochemicals, besides as being used as adsorbent for the wastewater treatment. This research aims to expand, in near future, the investigation field on these materials, with application in agriculture, increasing the interface between chemistry and agronomy.

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A cultura do milho é responsável pela produção de mais de 50 milhões de toneladas de grãos, apresentando o crescimento mais significativo da safra 2006 (Conab 2007. Esta é a principal cultura utilizada em rotação/sucessão com a soja, ABSTRACT RESUMOdestacando-se em área cultivada e produção, nas regiões Centro-Oeste, Sul e Sudeste, e com expressiva área no bioma Cerrado. O sistema plantio direto (SPD) tem se destacado como alternativa importante para a produção de grãos, devido à melhoria na qualidade do solo, associada à ciclagem de nutrientes, aumento da ativi-1. Trabalho recebido em jan./2010 e aceito para publicação em jul./2011 (n° registro: PAT 8706/

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