Scarification of Basalt Milkvetch (Astragalus filipes) Seed For Improved Emergence

Malheur Experiment Station

Information for Sustainable Agriculture

SCARIFICATION OF BASALT MILKVETCH (ASTRAGALUS FILIPES)

SEED FOR IMPROVED EMERGENCE

Clinton C. Shock, Erik B. Feibert, and Lamont D. Saunders

Malheur Experiment Station

Oregon State University

Ontario, OR 2007

Introduction

Basalt milk-vetch (Astragalus filipes) is a forb (non woody perennial) native to western North America. Basalt milk-vetch is a legume forb species of interest to revegetate rangelands of the intermountain northwest that can contribute high quality feed, valuable seed for wildlife, and nitrogen fixation to help maintain range productivity. Basalt milk-vetch has a hard seed coat that makes the seed impermeable to water and difficult to germinate. Low seed germination can contribute to low plant stand when seed is used to plant areas for seed increase. This trial tested basalt milk-vetch emergence in response to seed scarification intensity.

Materials and Methods

Basalt milk-vetch seed was collected from a highly productive plant that was planted at the Malheur Experiment Station. A scarification device was built by attaching 2 pieces of car tire inner tube to opposing sides of a drill bit. The drill bit was inserted into a cylinder made of 3 inch diameter PVC. The cylinder was lined with 220 grit sandpaper. The inner tube pieces were long enough to rub the sandpaper. The drill was rated at 2500 R.P.M., but testing measured 2050 R.P.M. The seed was placed in the cylinder and submitted to four durations of scarification (Table 1).

After the scarification treatments, 188 seeds were hand counted and planted manually in each plot at 0.25 inch depth on December 6, 2006. Each plot was one row 6.25 ft long. The plots were arranged in a randomized complete block design with four replicates. The plots were sprinkler irrigated to keep the soil surface moist from early April, 2007 to early May. On June 18, 2007, the emerged plants in each plot were counted.

Results and Discussion

The shortest scarification duration of 7.5 seconds resulted in the highest emergence, 10.8 percent (Table 1). The unscarified seed or seed scarified for 15 or 30 seconds resulted in significantly lower emergence than the seed scarified for 7.5 seconds. Emergence was low for all treatments.

When examined under the microscope, the seed was found to have many uneven edges. Scarification appeared to smooth some of the edges to different intensities depending on the duration.

Table 1. Emergence of basalt milk-vetch (Astragalus filipes) seed in response to scarification duration. Malheur Experiment Station, Oregon State University, Ontario, OR, 2007.