The present invention relates to a method for the preparation of a biological fertilizer comprising subjecting whey to a first fermentation step and the addition of a carrier material to the fermented whey and a biological fertilizer obtainable by the method. The biological fertilizer can be used as a replacement of the present artificial fertilizers thereby reducing many of the environmental problems associated with these artificial fertilizers. In addition, the biological fertilizer according to the present invention can be used in the field of biological agriculture for which, until the present biological fertilizer, no fertilizers were available.