First-Year Stand Decline in Birdsfoot Trefoil.

Birdsfoot trefoil (Lotus corniculatus L.) has long been used as forage in North America and has a similar distributional range as alfalfa (Medicago sativa L.). Birdsfoot trefoil is adapted to situations where defoliation is frequent, such as grazed pastures, because it maintains a higher amount of residual leaf area near the soil surface than alfalfa does. Cultivars of birdsfoot trefoil currently available to US livestock producers are not sufficiently persistent in the Eastern Transition Zone to be widely used. This research is part of the NIFA-AFRI project "Developing a trans-regional cultivar of birdsfoot trefoil". Our ultimate goal of the project is to develop a cultivar with high condensed-tannin concentration, wide geographic adaptation, and longer stand life than existing cultivars. Birdsfoot trefoil entries were seeded at 5 locations (Crossville, AL; East Lansing, MI; Lexington, KY; Mt Vernon, MO, and Kimberley, ID) in spring 2014. Stands counts were done after emergence, autumn 2014, spring 2015, and again in autumn 2015. All location except Kimberley, Idaho suffer rapid stand decline during the first year. Once the average population density falls below 2 plants per square foot, a synthetic population will be created from survivors for each location. At the southernmost location in Crossville, AL the critical stand density was already reached in August 2015. This was not unexpected, given the nature of abiotic and biotic stresses.