PH INFLUENCED BY THE ELEMENTAL COMPOSITION OF NUTRIENT SOLUTIONS

Nutrient solutions can be considered as aqueous solutions of inorganic ions. The pH of a nutrient solution is a property that is inherent to its composition. If another pH is aimed at, this can only be reached by changing the elemental composition. The pH of an aqueous solution i s determined by the initial concentration of acids and bases. In the c ase of nutrient solutions, this is dihydrogen phosphate (H2PO4-), bica rbonate (HCO3-) and/or ammonium (NH4+). In this study, formulas are de rived to calculate the pH of a nutrient solution as a function of the concentration of H2PO4-, NH4+, and/or HCO3-. The pH of a nutrient solu tion affects the dissociation, complexation, and precipitation reactio ns occurring in nutrient solutions. These chemical reactions significa ntly impact elemental speciation and bioavailability, and therefore, h ave to be taken into account in hydroponic plant nutritional research. The term ''speciation'' indicates the distribution of elements among their various chemical and physical forms like: free ions, soluble com plexes, chelates, ion pairs, solid and gaseous phases, and different o xidation states, all of which influences their reactivity, mobility an d bioavailability. A good knowledge of the chemical reactions occurrin g in nutrient solutions is the first prerequisite in hydroponic plant nutritional research. The pH of a nutrient solution is determined by i ts initial concentration of H2PO4-, NH4+, and HCO3-.