Poultry slaughter wastes (feathers, skin, bones, muscular tissue, fat, blood) were mineralized with 65% H(2)SO(4), neutralized with NH(3), modified by addn. of H(3)PO(4), NH(4)H(2)PO(4), K salts and ashes, granulated and dried to produce NPK(S) fertilizers contg. N 6-12%, P(2)O(5) 6-18%, K(2)O 7-12% and SO(3) 12-18% (bulk d. 900-1000 kg/m(3), grain strength 10-30 N). In some expts., the modified mixt. was added to stored manure to produce a suspension fertilizer (d. 1.5-1.65 kg/L, viscosity up to 1000 cP, pH 6.2-6.4) contg. N 8-12%, P(2)O(5) 5-6% and K(2)O 4-7%. The fertilizing activity of the products was tested on radish and cress seeds by measuring their germination ability. The fertilizers did not significantly differ in their usability (germination efficiency 65-95%). The emission of N compds. from the manure was considerably reduced.