|Wallace, John - Pennsylvania State University|
|Curran, William - Pennsylvania State University|
|Crockett, Ben - Pennsylvania State University|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/2015
Publication Date: 3/30/2015
Citation: Mirsky, S.B., Wallace, J.M., Curran, W.S., Crockett, B.C. 2015. Hairy vetch seedbank persistence and implications for cover crop management. Agronomy Journal. DOI:10.2134/agronj14.0523.
Interpretive Summary: Hairy vetch is an important cover crop that fits into a wide range of applications in temperate regions. This cover crop grows rapidly, produces tremendous levels of biomass (>6500 kg ha-1) rich in nitrogen, forms a dense weed suppressive mulch, reduces erosion and can inhibit soil-borne diseases. However, adoption of this cover crop has been greatly impeded due to farmer concerns as to the weediness of this cover crop. Hairy vetch can produce dormant seedbanks in the soil due to its hard seed and become a weed in winter annual cash crops such as wheat. A two-year field trial was established in Maryland and Pennsylvania to quantify how climate, variety, burial depth, and seed scarification influences hairy vetch emergence and seedbank persistence. Climate was not a strong determinant for hairy vetch persistence. Deeper burial of hairy vetch seed does decrease germination. Across all sites, varieties, burial depths, and year replications, scarification of hairy vetch seed resulted in no viability of hairy vetch in the soil after six months. These results have tremendous implications for the use of hairy vetch as a cover crop by farmers. Removing hairy vetch hard seed will greatly change farmer’s reluctance to use this cover crop. Furthermore, our results will inform seed companies on strategies to improve both their products and its sales.
Technical Abstract: Hairy vetch (Vicia villosa Roth) is a fast growing, winter hardy annual legume that can produce shoot biomass levels upwards of 6500 kg ha-1. This cover crop is well suited for summer annual grain rotations, as it fixes considerable amounts of nitrogen, reduces erosion through rapid ground cover, and suppresses weeds when used as a mulch. Despite the many agronomic benefits hairy vetch can provide, utilization as a cover crop has been limited due to producer concerns regarding the potential of hairy vetch to become a weed in subsequent crops. Hairy vetch weediness is attributed to its hard seed (1 to 21% of new cohorts of seed), a physical dormancy trait common to Vicia species. A 2-yr field experiment was conducted in Pennsylvania and Maryland to characterize the effects of mechanical scarification (vs. control) and burial depth (3 cm vs. 15 cm) on hairy vetch seedbank dynamics using two commonly used varieties. Experimental units consisted of seed burial cages that were excavated 6, 12 and 18 months after burial. Field and laboratory measurements were conducted to determine seedbank fate: seedling emergence, seedbank persistence and seedbank loss measured as a percentage of the initial viable seedbank. Hairy vetch emergence and persistence in the soil seedbank varied considerably across varieties, years and study locations. However, seed that received scarification consistently eliminated seedbank persistence beyond 6 months after burial. Among non-scarified seed treatments, seedbank persistence ranged from <1 to 7% 6 months after burial and further declined (<1 to 4%) 12 months after burial. Deep seed burial (15 cm) resulted in decreased seedling emergence and increased seedbank loss in comparison to the simulated planting depth (3 cm). Among treatments, seedling emergence ranged from 36 to 84% at the 3 cm depth and 7 to 46% at the 15 cm depth. Seed mortality due to fatal germination or decay ranged from 15 to 64% at the 3 cm depth and 47 to 92% at the 15 cm depth. These results indicate that mechanical scarification prior to planting is a promising strategy for managing hairy vetch seedbank persistence and warrants further investigation. Targeted tillage may also be an effective tool for decreasing hairy vetch seedbanks when coupled with other management tactics.