Effect of NPK fertilisation on the amino acid composition of wheat grain yields

The individual amino acid contents of wheat seeds from long-term NPK fertilizer trials grown on strongly calcareous and humus-rich meadow soil in 1991 were examined with the RP HPLC method, in order to determine the effect of increasing NPK supplies. Higher N doses increased the amounts of ASP, GLU, SER, HIS, GLY, THR, ARG, ALA, TYR, VAL, PHE, ILE, LEU and LYS by 14-36%. The highest values were obtained at a fertilizer level of 180 kg N/ha, except for ARG and HIS. Increased PK doses significantly decreased the quantities of ASP, GLU, SER, HIS, GLY, THR, ARG, ALA, TYR, CYS, VAL, PHE, ILE and LEU. When N and PK were applied together, the amounts of amino acids did not change to such an extent as in the case of separate N or PK doses. The two wheat varieties studied showed significant differences only in the amount of SER, CYS and PHE.