Hello Gardeners, I’m Amanda McNulty with Clemson Extension and Making It Grow. Controlled slow release, water-insoluble nitrogen, urea formaldehyde, sulfur-coated urea. These terms describe fertilizers that release nutrients to plants over an extended period of time as opposed to old-fashioned, quick release fertilizers. The advantage of quick release fertilizers is price – but it may be a false savings as they can burn plants and in heavy rainfalls, you can lose nutrients to leaching and run