Mechanical Scarification and Soil Depth Affect Hairy Vetch Seed Bank Persistence.

Hairy vetch (Vicia villosa Roth) is an important legume cover crop used in the Northeast. It is valuable for nitrogen fixation, weed suppression, and erosion control. However, adoption of hairy vetch by some producers has been limited for various reasons including the perception that it can become an invasive weed. Weediness can occur with hairy vetch due to physical dormancy resulting from hard seed. The focus of this project was to quantify seedling emergence and soil seed bank persistence of hairy vetch over time as influenced by soil burial depth, seed cultivar and mechanical seed scarification. Experiments were conducted from 2009 to 2011 at the Rock Springs Agronomy Farm in Centre County, PA and the Beltsville Agricultural Research Center in Beltsville, MD. A seed burial study was initiated fall of 2009 where 500 seeds of three hairy vetch cultivars (Albert Lea, Groff, Nebraska) were placed at the bottom of mesh cages at two burial depths (3 and 15 cm) with a mechanical scarification treatment (scarified vs. non-scarified). Cages were excavated at three time intervals (6, 12, 18 months). The experiment was structured as a split-split-plot with four replications. Emerged seedlings were counted every two weeks and ungerminated seed was collected at each excavation date. Persistent hairy vetch seedbanks were tested for viability. Scarified treatments contained no viable seed after six months at both locations while non-scarified treatments had a maximum of 7.9%. Nearly all observed emergence occurred within six months. Seed at the 15 cm depth decreased in emergence by 24% over sites and showed an increase in seed bank persistence (max. 2.4%) compared to the 3 cm depth. Mechanical scarification of hairy vetch prior to planting has potential to eliminate seed bank persistence without lowering emergence.