| Popis: |
Forage production from Rocky Mountain meadows is characteristically low, averaging 1.3 ton/acre. Research has shown that lack of N fertilization is a major factor limiting yield. Little research has compared N fertilizer sources, rates, and application time for meadow pastures. Experiments were conducted on a less productive Edlin sandy loam soil (coarse-loamy, mixed Borollic Camborthids) located near Saratoga, WY, and on a more productive Mayoworth sandy clay loam soil (fine, montmorillinitic Argic Cryoborolls) near Gannby, CO, over 3 yr. Treatments consisted of factorial combinations of two application times (fall and spring), five N rates (0, 50, 100, 150, and 200 lb N/acre), and two N sources (ammonium nitrate [AN] and urea). Forage production increased from 1.1 ton/acre with no N fertilizer to 3.4 ton/acre on the Edlin soil and from 2.7 ton/acre to 4.9 ton/acre on the Mayoworth soil with 150 lb N/acre as AN. Optimum economic N rate varied with source, time of application, and most importantly, with yield potential of the soil. Ammonium nitrate consistently produced more forage and higher fertilizer recovery efficiency than urea at equal N rates. Spring N application produced higher yields and higher fertilizer recovery efficiency than fall application on the more productive Mayoworth soil. On the Edlin soil, time of application did not affect forage production. Fall application may be necessary, however, where mountain meadows are wet during the spring fertilization period, preventing access to fertilizer application equipment. For fall application, AN should be used as the N source, since AN provided the highest yield and fertilizer recovery efficiency. On the Edlin soil, 150 lb N/acre spring-applied increased protein from 7.1 % to 8.7 % and 9.2 % for urea and AN, respectively. On the more productive Mayoworth soil, forage protein concentration increased less dramatically with similar N application rates. If producers are interested in producing quality forage, adequate N fertilization is vital |
