There are many types of fertilizer available for purchase, and it can be quite confusing trying to choose the correct one. Understanding the nutrient requirements of the grass as described above will help narrow the choices. Understanding the different types of fertilizers, will help narrow the choices even further.
Fertilizers can be divided into two major groups, fast release and slow release. This refers to how quickly the nitrogen is released and made available to the plant. You may also have heard about organic vs. inorganic fertilizers. This refers to the chemical composition of the fertilizer. It is important to understand that the term “organic” means the fertilizer contains carbon in the chemical structure. Organic fertilizers include natural materials such as sewage-based products like Milorganite®, animal by-products like manures and bone meals, and plant by-products like corn gluten meal. There are also synthetic organics like urea which is very common in the agricultural industry, but less so in the turf industry because of its very fast release and high burn properties. There are, however, also many forms of urea that have been developed to slow its release and lower its burn potential.
Fast-release fertilizers are quickly released into the soil and available for uptake by the plant. The advantages of these materials are that they are relatively inexpensive, are not dependent on temperature for release and give the grass a quick response. The disadvantages of fast-release fertilizers are that they are more likely to burn the turf if applied incorrectly (during hot periods or at too high of a rate), the response is generally short lived, and because of their water solubility they are more likely to leach through sandy soils or runoff of compacted soils. Several light applications can compensate for the quick, short-lived response, but this requires more labor.
Slow-release fertilizers cause a more uniform color and growth response over a longer period of time than the fast-release fertilizers. They are also less likely burn the grass. Some products will release nitrogen into the soil slowly over several weeks or even months. All the natural products like manures, bone meals, etc. are slo- release fertilizers and require soil microbes to release the nitrogen to make it available to the plant. When applied to cool soil temperatures, below 50° F, the grass may not respond at all to the application. Most of the natural slow-release fertilizers are quite low in nitrogen content so it will take more product to apply the same rate of actual nitrogen as it would with a synthetic fertilizer with a higher nitrogen content. Other types of slow-release fertilizers include sulfur-coated urea, polycoated urea and other urea based products. These products tend to be more expensive, but provide a good uniform turf response.