Nutrient composition for biological systems

A nutrient composition for biological systems, such as humans, animals, plants and microorganisms, which comprises at least one monometallic or mixed metallic phosphate of the type (M1 M2 M3 . . . Mx)3(PO4)2.aH2O, where 0≦a≦9, wherein (M1, M2, M3 . . . Mx) represent the one metal of the monometallic or the several metals of the mixed metallic phosphate and are selected from Na, K, Mg, Ca, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn and B, with the proviso that at least one of the metals in the phosphate is selected from Mn, Fe, Co and Ni, wherein the at least one phosphate can be prepared or is prepared by

• a) preparing an aqueous solution (I) which comprises at least one or more of the metals Mn, Fe, Co and/or Ni as divalent cations by introducing oxidic metal(II), metal(III) and/or metal(IV) compounds or mixtures or compounds thereof having mixed oxidation states, selected from hydroxides, oxides, oxide hydroxides, oxide hydrates, carbonates and hydroxide carbonates, of at least one of the metals Mn, Fe, Co and/or Ni together with the elemental forms or alloys of at least one of the metals Mn, Fe, Co and/or Ni into an aqueous medium comprising phosphoric acid and reacting the oxidic metal compounds with the elemental forms or alloys of the metals (in a redox reaction) to give the divalent metal ions,
• b) separating off any solids present from the phosphoric acid aqueous solution (I),
• c) if the phosphate is a mixed metallic phosphate and, in addition to the metals introduced into the solution in stage a), comprises further metals selected from (M1, M2, M3 . . . Mx), furthermore adding to the aqueous solution (I) at least one compound of at least one of the metals (M1, M2, M3 . . . Mx) in the form of an aqueous solution or as a solid in the form of a salt,
• d) providing an initial charge solution (II) having a pH of from 5 to 8 prepared from an aqueous phosphoric acid solution by neutralization with an aqueous alkali metal hydroxide solution or prepared from an aqueous solution of one or more alkali metal phosphates,
• e) metering the aqueous solution (I) into the initial charge solution (II) and simultaneously metering in a basic aqueous alkali metal hydroxide solution such that the pH of the reaction mixture obtained is kept in the range of from 5 to 8,the phosphate of the type (M1 M2 M3 . . . Mx)3(PO4)2.aH2O being precipitated,
• f) separating off from the reaction solution the phosphate which has precipitated.