W163 Nitrogen Sources for Pasture and Hay

Nitrogen is one of the major nutrients required by forage grasses for proper growth and development. Yield and forage quality response to added nitrogen can be dramatic. Unlike the other two major nutrients, phosphorus and potassium, nitrogen is not retained in the soil from year to year in a form that forage plants can readily use. Nitrogen applied to the soil is rapidly converted to nitrate-N and is then often incorporated into organic materials, leached out of the rooting zone by rainfall or lost back to the atmosphere. Nitrate-N is rapidly available to the forage plant but, especially in lighter soils, moves with the soil water out of the croprooting zone. In wet or poorly drained soils, the nitrate-N can be converted back to gaseous forms and lost to the atmosphere. Urea nitrogen on the soil surface is subject to volatilization loss as ammonia.

Nitrogen can be supplied to forage grasses by accompanying legumes such as clovers or alfalfa, which can fix nitrogen directly from the atmosphere. In forage systems without legumes and in some legume grass management schemes, nitrogen must be added as a fertilizer material to achieve the best forage grass production and quality. Several types of nitrogen fertilizer materials are available. The best one for you will depend on factors such as fertilizer material availability, price, equipment available, time of year and tillage practice.