N2 Fixation of Common and Hairy Vetches when Intercropped into Switchgrass

Abstract

Interest in sustainable alternatives to synthetic nitrogen (N) for switchgrass (Panicum virgatum L.) forage and bioenergy production, such as biological N 2 fixation (BNF) via legume-intercropping, continues to increase. The objectives were to: (i) test physical and chemical scarification techniques (10 total) for common vetch (Vicia sativa L.); (ii) assess whether switchgrass yield is increased by BNF under optimum seed dormancy suppression methods; and (iii) determine BNF rates of common and hairy vetch (Vicia villosa L.) via the N-difference method. Results indicate that chemical scarification (sulfuric acid) and mechanical pretreatment (0.7 kg of pressure for one minute) improve common vetch germination by 60% and 50%, respectively, relative to controls. Under optimum scarification methods, BNF was 59.3 and 43.3 kg·N·ha −1 when seeded at 7 kg pure live seed ha −1 for common and hairy vetch, respectively. However, at this seeding rate, switchgrass yields were not affected by BNF (p > 0.05). Based on BNF rates and plant density estimates, seeding rates of 8 and 10 kg pure live seed (PLS) ha −1 for common and hairy vetch, respectively, would be required to obtain plant densities sufficient for BNF at the current recommended rate of 67 kg·N·ha −1 for switchgrass biomass production in the Southeastern U.S.

Impact of priming on seed germination, seedling growth and gene expression in common vetch under salinity stress

“…Common vetch is a forage legume that is moderately sensitive to soil salinity and is damaged by high salinity (34,35). Certain pre-treatments before sowing can increase germination of common vetch (30,36). Unfortunately, priming studies of common vetch under stress conditions are limited.…”