AGRONOMIC NEWS ITEMS
From Agronomists of the
Potash & Phosphate Institute
655 Engineering Drive, Suite 110
Norcross, Georgia 30092-2837
Phone (770) 447-0335
Winter 1997, No. 3
Nitrogen fertilizers used on turf may be classed as quick release or slow release. Common quick release sources include ammonium sulfate, urea, and ammonium nitrate. The most effective way to apply quick release nitrogen fertilizers is by applying low rates frequently. Slow release nitrogen sources provide more uniform turfgrass growth and performance with fewer applications.
There are many slow release sources of nitrogen commonly used on turf. An understanding of the mechanisms of release of nitrogen from these sources and the factors that affect that release is essential when selecting the best source for a specific situation. Following is an overview of common slow release nitrogen sources and their characteristics.
Coated Nitrogen Sources
There are many natural organic nitrogen sources available for use on turf, including sewage sludge and animal manures.
Stabilized Nitrogen Sources
Before nitrogen from urea becomes plant available, the urea must undergo hydrolysis. Urea hydrolysis is a urease enzyme driven reaction. Urease inhibitors, such as NBPT, slow the rate of hydrolysis of urea fertilizer, resulting in a lower potential for gaseous loss of nitrogen from surface applied urea. Nitrification inhibitors, such as DCD, slow the conversion of ammonium-nitrogen to nitrate-nitrogen in soils. Ammonium is less susceptible than nitrate to leaching and denitrification losses. Urea, and the resulting ammonium, that is treated with these compounds is usually more stable in the soil than urea alone. Consequently, these materials may provide a prolonged nitrogen response.