Figure Phosphorus and potassium release behavior were similar for the precursor (KH2PO4) and milled samples, but slower for milled samples, this fact shows that the phosphates obtained by milling improve the nutrients management maintaining their bioavailability. On the other hand, calcium release is rather different for eggshell to the milled samples. Even that CaCO3 in the eggshell may be soluble in acids, the kinetic was extremely slow in comparison, evidencing the solubility of phosphates formed.