Forages and Pastures: Grazing and Forage Management

The objective of this study was to compare summer annuals for fall and winter grazing on irrigated pastures in the Intermountain West. The cool desert areas of this region have short growing seasons (≤120 d) with high daytime temperatures and cool nights resulting in sufficent growing degree days, but impaired production on cool season forages during late summer. Five species were planted in Carmen, ID (45°17′N, 113°53′W; 1155 m elevation) in 0.10 ha plots with 3 plot replicates per species. Four species were planted in yr 1 and 2: CORN (Zea mays), sorghum x sudangrass (Sorghum spp; SUDEX), TEFF (Eragrostis tef), and GERMAN foxtail (Setaria italica). PEARL millet (Pennisetum glaucum) planted in yr 1 was replaced by PROSO millet (Panicum miliaceum) in yr 2. All species except TEFF were planted no-till from June 25 to July 2. TEFF was planted after minimum tillage. Three 1/1000 ha yield samples were taken from each plot. Pooled samples for each species were analyzed for CP, ADF, NDF, Ca and P. TEFF was sampled at 50 d post planting (haying) with all species sampled after killing frost (September 8 and 16, yr 1 and 2, respectively). Heifers grazed the plots during November and December, and animal grazing days were recorded. Yield data were analyzed by ANOVA with means compared using a t-test. Data for each yr were analyzed separately. Species affected DM yield (P = 0.10 yr 1; P < 0.02 yr 2). Yields (DM; Mg ha−1) were not different (P = 0.22) for CORN (5.5 ± 1.6, 10.7 ± 1.0), GERMAN (5.4 ± 0.4, 5.8 ± 1.0), and SUDEX (7.0 ± 0.7, 7.1 ± 1.8) in yr 1 and 2, respectively, and TEFF (6.1 ± 0.2; yr 1 only). In yr 1, yields of SUDEX and TEFF exceeded (P < 0.01) PEARL (3.9 ± 1.2 Mg ha−1). CORN yields were greater (P < 0.01) than GERMAN or PROSO (3.9 ± 1.6 Mg ha−1) in yr 2. Nutrient content of all forages exceeded NRC requirements for cows in mid-gestation. TEFF, PROSO, and PEARL produced fewer (P = 0.10) animal grazing days than the other species. In conclusion, CORN, SUDEX, and GERMAN produce acceptable fall and winter grazing for the Intermountain West.