The professional range of controlled release nutrients from the Scotts Professional Range. Osmocote is an organic resin coated fertiliser with every granule containing the following NPK – 15+9+12 which is released slowly over the growing period up to 6 months. Plants grow better because they get the nutrients they require when they want it. The leaching of nutrients is minimised by the resin coating. I mixed Osmocote Exact Standard into my leek mixture in 25 litre pots and had the best leeks for many years. 1kg sufficient for 25sqm of soil or 220g per 70 litre bag or 3g per litre.