Location: Forage and Range Research2012 Annual Report
1a. Objectives (from AD-416):
1. Determine the best seed treatments to maximize germination in basalt milkvetch and western prairie clover. 2. Identify the most appropriate planting depths and seasons that will give the best establishment success for the two legume species. 3. Assess how seed sources will establish across genetic structures and environmental gradients for basalt milkvetch and western prairie clover.
1b. Approach (from AD-416):
l. Determine the best seed treatments to maximize germination: Hard seededness is a common feature in legume species, which limits initial, uniform germination and subsequent establishment. The effects of various seed treatments (mechanical scarification, acid scarification, boiling water treatment, and control) and age of seed (newly harvested up to one-year-old seed) will be investigated for each of the major seed sources of the three legume species. All combinations of these treatments will be tested in a greenhouse to determine which combination of treatments yields the best germination and seedling establishment. 2. Identify planting depths and seasons that will give the best success: Given the data obtained from Objective 1, the best treatment combination will be used in actual field evaluations. Seeds from each species and source will be planted with either a walk-behind drill seeder or a RoughRider range drill. Replicated fall dormant plantings will be compared with spring plantings and tested twice at each of several locations. First and second year establishment/survival will be recorded at each of the test sites. 3. Assess how seed sources will establish across genetic structures and environmental gradients: Up to three locations will be planted for each species. Locations for western prairie clover and basalt milkvetch will be at sites in Oregon, Idaho, and Nevada. Locations for Searls prairie clover will be in northwest and southern Utah and Nevada. Exact test locations will be coordinated with the BLM and USFS, or the USDA-ARS Area-Wide Project, and plots will be protected from grazing. The exact locations will be situated to span genetic structures as well as the environmental gradients shown to be most highly correlated with collection sites. Establishment data will be collected for two years post-planting, but sites will be kept to allow for long-term observation.
3. Progress Report:
Greenhouse experiments were conducted to determine the effect of seed scarification, soil type, and raindrop droplet size on the emergence of seedlings of basalt milkvetch (Astragalus filipes), western prairie clover (Dalea ornata), and Searls’ prairie clover (Dalea ornata). Treatments included two scarification treatments (acid-scarification, no seed treatment), three soil types (sand, sand/clay, clay), and two water droplet sizes (small, large). Results showed that scarification was critical for effective seedling emergence in all three soil types for western and Searls’ prairie clover, but that scarification did not improve emergence in basalt milkvetch. Also, a larger water droplet size caused soil to crust and reduced emergence more than the smaller droplet size. As a result, seed scarification is critical for effective seedling establishment in the two prairie clover species, but other seed treatments will be necessary to maximize seedling establishment in basalt milkvetch. Field plots of acid-scarified and non-scarified seeds of basalt milkvetch and western prairie clover were seeded at Powell Butte and Clarno in Central Oregon with a single-row seeder in October 2011 and April 2012 with collaborators from the U.S. Forest Service. Seeded plots were also established with cooperators at Oregon State University’s Malhuer Experiment Station at Ontario. Seedling emergence at the three Oregon sites was routinely monitored and showed that acid-scarified seed of the two prairie clover species emerged considerably better than non-scarified seed. However, acid scarification did not improve seedling emergence of basalt milkvetch. As a result, seed of the two prairie clover species will need to be scarified prior to seeding to maximize seedling establishment; however, other treatments will be needed to improve seedling establishment of basalt milkvetch.