Quick-release nitrogen sources are also called "quickly available," "fast-acting," "soluble," "readily available," and other terms that indicate rapid availability of nitrogen to turf after application. This group includes compounds containing ammonium, nitrate, or urea. Quick-release sources have nitrogen contents ranging from 11 to 46 percent (Table 3) and generally are less expensive than slow-release sources. Being water soluble, they may be applied in liquid as well as in dry form. They give a rapid green-up response, and frequent applications at low rates are suggested for reducing excessive growth, fertilizer burn, and nitrogen loss to the environment. Quick-release nitrogen sources are often combined with slow-release sources to provide a fast but moderate green-up and growth response while extending the duration of the response.