Population growth and the growing need for food require greater efficiency in the use of nitrogen (N), phosphorus (P) and potassium (K) present in fertilizers, which can be increased through the development of composites that slowly release N, P and K. To obtain the composite, bentonite and illite clays, LTA zeolites and clinoptilolite were tested as potassium carriers. The materials were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR). The leached potassium content in soil columns was determined by inductively coupled plasma atomic emission spectrometry (ICP-OES). Among the materials tested, LTA zeolite showed the best potassium adsorption capacity, with a slow and gradual release behavior. LTA zeolite together with hydroxyapatite and urea constitute the synthesized composites that were characterized by XRD, XRF, FTIR and scanning electron microscopy (SEM-FEG). XRD analysis with Rietveld refinement confirmed that the composite samples present hydroxyapatite in two monoclinic and hexagonal phases, in addition to the phases referring to zeolite LTA and urea, which are also confirmed by the FTIR and SEM results. The SEM images show the rod-shaped hydroxyapatite-urea crystals lining the cubic surface of the zeolite LTA.