The present application relates to a combined NPK-Si fertilizer product comprising a mineral NPK fertilizer, which comprises at least one nutrient compound of nitrogen, phosphorous or potassium, and a particulate amorphous silicon dioxide, wherein the ratio of the mineral NPK fertilizer to the amorphous silicon dioxide is from 10:90 to 90:10, based on the dry weight of the at least one nutrient compound of nitrogen, phosphorous or potassium, and the amorphous silicon dioxide contained in the product. The application also relates to the method of production of the inventive NPK-Si fertilizer.