Paper presents the structure solutions of a fertilizer bulk blending plant designed and tested by the Fertilizer Research Institute (Instytut Nawozów Sztucznych). Weight feeder and drum mixer are the main assemblies of the plant. The operation parameters of blending plant were fitted to the requirements of firms manufacturing fertilizer blends. The qualitative evaluation of home-made granular fertilizers usable for blend production on mechanical way was carried out on the basis of screen analyses. The evaluation method based on mathematical criteria developed in the USA and Canada (SGN = size guide index; Ul = uniformity index) was presented. The values of both indices were calculated for the following fertilizers: nitro-chalk, triple superphosphate, ammonium phosphate, granular potsh salt; principles for practical application of the results were given as well. The bulk blending plant according to Institutes’ design, equipped with fertilization optimizing programme and blend composition programme, may render complex fertilizing services for the farmers. In comparison to traditional fertilization system the production of fertilizer blends by using described method is of measurable advantage.