NITROGEN-FERTILIZATION OF MOUNTAIN MEADOWS

Forage production from Rocky Mountain meadows is characteristically lo w, averaging 1.3 ton/acre. Research has shown that lack of N fertiliza tion is a major factor limiting yield. Little research has compared N fertilizer sources, rates, and application time for meadow pastures. E xperiments were conducted on a less productive Edlin sandy loam soil ( coarse-loamy, mixed Borollic Camborthids) located near Saratoga, WY, a nd on a more productive Mayoworth sandy clay loam soil (fine, montmori llinitic Argic Cryoborolls) near Granby, CO, over 3 yr. Treatments con sisted of factorial combinations of two application times (fall and sp ring), five N rates (0, 50, 100, 150, and 200 lb N/acre), and two N so urces (ammonium nitrate [AN] and urea). Forage production increased fr om 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 a pplication, and most importantly, with yield potential of the soil. Am monium 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 s oil, time of application did not affect forage production. Fall applic ation may be necessary, however, where mountain meadows are wet during the spring fertilization period, preventing access to fertilizer appl ication equipment. For fall application, AN should be used as the N so urce, since AN provided the highest yield and fertilizer recovery effi ciency. On the Edlin soil, 150 lb N/acre spring-applied increased prot ein from 7.1% to 8.7% and 9.2% for urea and AN, respectively. On the m ore productive Mayoworth soil, forage protein concentration increased less dramatically with similar N application rates. If producers are i nterested in producing quality forage, adequate N fertilization is vit al.