Location: Forage and Range Research2011 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 studies were conducted that examined age of seed (newly harvested, two-year old seed), depth of planting (0.6 cm, 1.9 cm), and seed treatment (acid scarification, mechanical scarification, control). Results showed that scarification greatly improved emergence in western and Searls' prairie clover, but less so for basalt milkvetch. Also, seedlings of the two prairie clover species emerged well at the 1.9-cm depth. Additional greenhouse studies will be conducted this winter to determine the best combinations of treatments to maximize germination and establishment. Results from greenhouse studies will be used to design establishment experiments in the field.