Milorganite® 49028 50 lb Bag Milorganite® 6-4-0 Professional. Milorganite® has been made for over 95 years and is the leading slow-release nitrogen fertilizer in North America. Milorganite® is a proven, reliable, and safe slow-release nitrogen fertilizer. Milorganite® professional products are only available in full truckloads (21 tons) sold through our distribution network to the golf and professional landscape markets.