The nutrient content of the samples and precursors were obtained dissolving the samples by using acid digestion in H2SO4/H2O2 PA mixture (8:1 v/v, by 24 h at 250 °C), and determined by atomic absorption (K and Ca) and colorimetric (P) methods (Table , Supplementary Materials). Before release essays at citric acid solution (2 wt%), the material has been pelletized to simulated commercial products. The pellets were obtained in steel pelletizer applying the pressure of 5 bar, and the weight was standardized to 100 mg/L of P. One single pellet were used in each essay in triplicate, that was placed in 10 mL beaker, this small beaker was immersed into 300 mL of 2% citric acid solution in a 600 mL beaker, the system was kept closed with polyvinyl chloride (PVC) film, in a constant temperature room at 25 °C and under a magnetic stirring. The stirring ensures homogeneous distribution of diffused elements, and aliquots of 1.2 mL at different times (from 15 min to 30 days) have been collected to evaluate the release behavior and allow the calculation of a release kinetic model of Ca, K and P.