"Growing birdsfoot trefoil (Lotus corniculatus L., BFT) in mixtures with tall fescue [Schedonorus arundinaceus (Schreb.) Dumort] may help livestock neutralize toxic alkaloids in endophyte-infected tall fescue, but little is known about condensed tannin (CT) concentrations of such mixtures. Therefore, I evaluated forage yield and quality, CT concentration, soil microbial activity, and root morphology of BFT-tall fescue mixtures grazed by sheep in Lansing, MI. Mixtures contained eight BFT cultivars with a range of CT concentrations and four tall fescue cultivars varying in endophyte infection status. The BFT proportion of forage mixtures declined from > 95% to < 10% from 2015-2016 due to reduced stand density of BFT. Mixtures with Oberhaunstädter BFT expressed greater CT concentrations, with levels from 7.5 to 31.7 g kg-1 , and 70% greater stand density in 2016 than all other mixtures. Nutritive value and pregrazing forage yield was always adequate for ewes at maintenance, regardless of CT concentration or endophyte type. Therefore, high-tannin Oberhaunstädter in mixtures with endophyte-free tall fescue proves most suitable for forage production in south-central Michigan. Belowground processes were influenced more by variability between grazing seasons than by CT or endophyte type; cumulative C mineralization was greater in 2015 whereas root traits associated with superior resource acquisition (root length density, specific root length, root surface area density) were greater in 2016. This provides insight for future studies to further evaluate the effects of secondary compounds in forage crops on belowground dynamics."--Page ii.
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