The present invention relates to a process of producing organic-mineral fertilizers having a biostimulating action and which may be used in market gardening, in orchards, in cultivation of field crops and ornamental plants, lawns, etc., and are intended for a soil application and/or for a foliar application and/or for a drop- irrigation (fertigation). The present invention also relates to fertilizers produced by this process. In order to produce in a one integrated technological process an organic-mineral fertilizer with an improved quality, which would increase a yield of plants, the process according to the present invention comprises the steps of a) heating a protein hydrolysate obtained in an enzymatic hydrolysis of animal tissues comprising a natural free α-L-amino acids in an amount of at least 4 % by weight, up to a temperature higher than 70°C and at a pressure within the range from 0.3 to 0.9 bar, until obtaining a content of natural free α-L-amino acids amounting at least 6 % by weight, preferabl
