2017 ASHS Annual Conference

Legumes have important roles in rangeland ecosystems and they may be scarce in degraded landscapes. Seeds of legumes are needed for rangeland restoration in the Intermountain West. Since relatively little is known about the water needs for seed production of potentially useful legumes (Dalea ornata, Dalea searlsiae, and Astragalus filipes), irrigation trials were conducted over multiple years. The three species grown at the Oregon State University Malheur Experiment Station, Ontario, Ore. received 0, 100, or 200 mm of irrigation per year. Seed yield responses to irrigation were evaluated by linear and quadratic regression over the applied water rates. In order to improve the accuracy of estimated irrigation water requirements in any given year, regressions were also run on seed yield responses to irrigation plus precipitation during the previous spring; spring and winter; and spring, winter and fall. Adding spring, winter, and fall precipitation to applied water improved the accuracy of estimated water requirements for maximum seed production of D. ornata and D. searlsiae. For D. ornata the highest yields averaged 396 kg•ha^–1 and ranged from 146 to 545 kg•ha^–1. Averaged over 6 years, seed yield of D. ornata was highest with 393 mm of spring, winter, and fall precipitation plus irrigation. For D. searlsiae, the highest yields averaged 260 kg•ha^–1 and ranged from 51to 424 kg•ha^–1. Averaged over 6 years, seed yield of D. searlsiae was highest with 412 mm of spring, winter, and fall precipitation plus irrigation. Seed yields of A. filipes ranged from 7 to 110 kg•ha^–1 depending on year and averaged 40 kg•ha^–1 over six years. Seed yields of A. filipes did not respond to irrigation in any of the six years.