Forage Yield, Quality, and Root Characteristics of Birdsfoot Trefoil-Tall Fescue Pastures.

Birdsfoot trefoil (Lotus corniculatus L.; BFT), a perennial forage legume containing bioactive condensed tannins (CT), has the capability of yielding productive pastures when grown with a perennial companion grass; however, the effect of grass-legume mixtures on below-ground productivity remains unknown. We are investigating the interaction between BFT CT content and tall fescue (Schedonorus arundinaceus (Schreb.) Dumort.; TF) endophyte infection status on forage yield, quality, and root characteristics in East Lansing, Michigan. Experimental design was a RCBD with a split-split plot treatment arrangement (n=2). Main plot was TF variety (‘Kentucky 31’, ‘Martin 2’), subplot was endophyte infection status (E+, E-), and sub-subplot was eight BFT seed sources with varying CT (‘Common’, ‘Bull’, ‘Bruce’, ‘Pardee’, ‘Oberhaunstädter’, ‘AC Langille’, two sources of ‘Norcen’). BFT was planted July 2014, overseeded with TF in March 2015 and re-planted August 2015 due to poor grass establishment. In 2015, all plots were subjected to three high-intensity, short-duration grazing events with sheep. Forage biomass was estimated nondestructively using a rising plate meter. Root samples from four BFT cultivars were collected to a 15-cm depth in September 2015 and analyzed using WinRhizo software. Stands contained little grass prior to replanting. Available forage biomass exceeded 2.9 Mg ha^-1 for all grazing events. Nutritive composition of harvested forage was always adequate for pastured sheep. Crude protein was lower for Oberhaunstädter than the average of all other cultivars (15.8 vs 17.0, 14.7 vs 17.0, 16.0 vs 17.5 g kg^-1 for grazing events 1, 2 and 3, respectively). Root samples indicated a below-ground interaction in root volume and surface area between BFT and TF cultivars. There was also an interaction in soil respiration (Solvita CO₂-Burst) between BFT and TF cultivars. Results show multiple interactions between BFT and TF cultivars affecting above- and below-ground productivity.