The harvest method will influence considerably the amount of N used. With hay harvest, all forage is removed from the field, so large amounts of N are taken out of the field, and there is only limited recycling of nutrients. Since high yields customarily are desired with hay production, recommendations for hay N fertilization usually are in the range of 134 to 224 kg N/ha/yr (120-200 lb N/acre/yr). These applications can be split, with 67 to 199 kg N/ha (60-90 lb N/acre) applied at the onset of the growing season, a second application of 50 to 67 kg/ha (45-60 lb/acre) applied after the first hay cut if at least 1 mo remains in the spring growing season, and another 67 kg/ha (60 lb/acre) in the fall to stimulate growth (see Stockpiling section in this chapter).

For pastures, the N recommendations rarely are similar to those for hayfields. However, it is important that N fertilization matches the forage requirements for the enterprise. There is no reason to apply high N rates if the forage that will be produced cannot be used adequately. Since the primary growth response to N application typically will occur in a 2- to 4-wk period following fertilization, N applications should be limited so that the excess growth will not be wasted. If excess growth early in the season cannot be harvested for hay, practical experience has shown that spring N fertilization for pastures can be reduced to one-half of the amount used for hayfields. If pastures will have a heavy stocking density during spring, resulting in a high forage requirement, N application may be increased. If stocking density and forage requirements are low, then spring N rates can be reduced or eliminated.


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