Submitted to: Journal of Range Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 16, 1991
Publication Date: N/A
Interpretive Summary: Many livestock producers and advisors believe that the Crested Wheatgrass 'P-27' maintains its forage quality later into the season than do cultivars like Nordan. The study was conducted at Logan, UT and showed that quality in all of the wheatgrasses declined by mid-summer. The P-27 and other selections within Agropyron fragile had lower dry matter digestibility and dry matter yield than other Agropyron desertorum or A. cristatum entries. These findings are contrary to expectations.
Technical Abstract: Crested wheatgrasses (Agropyron spp.) are grown on 6 million ha in the U.S. and Canada, where they provide excellent early-season forage, but lose nutritional quality by midsummer. Some producers believe that A. fragile maintains its quality longer than other crested wheatgrasses. This study compared herbage yield and quality of 3 A. fragile entries with A. desertorum, A. cristatum, I-28 (induced tetraploid of A. cristatum), and the hybrid 'Hycrest'. Entries were established near Logan, UT., on 1-m spacings. Herbage yield and quality were determined in year 2 and 3 at vegetative, boot, flower, seed ripe, and post-seed- ripe maturity stages (harvests 1 through 5) and on regrowth following the vegetative and boot-stage harvests. All entries flowered within 1 to 2 days of each other. Dry-matter yield increased for all grasses, but digestibility (IVDMD), crude protein, and elemental concentrations declined with maturity. Mean IVDMD values for all grasses were 741, 642, 534, 485, and 444 mg g-1 for harvests 1 through 5 and 490 and 560 mg g-1 for the regrowth following harvest 1 and 2. The A. fragile entries had higher N, Ca, P, and Ca/P, but lower yield, IVDMD, and grass tetany potential values than other Agropyrons. Contrary to expections, IVDMD of A. fragile decreased to 500 mg g-1, 6 to 11 days earlier than for the other Agropyrons. The I-28 and Hycrest entries had higher yield, IVDMD, K, and grass tetany risk and lower N, Ca, P, and Ca/P than the other Agropyrons.