Garden fertiliser. Polarised light micrograph of crystals of a garden fertiliser. This water- soluble product is used by amateur gardeners as a general plant fertiliser. The product contains 15% nitrogen, 30% phosphorus and 15% potassium; it also has trace amounts of iron, manganese, copper, zinc, boron and molybdenum. Magnification: x10 at 35mm size. ICI Miracle-Gro" fertiliser."