Winter-kill of alfalfa (Medicago sativa L.) causes substantial yield losses in northern environments, requiring alternative forages to meet livestock needs. This study explores the forage yield, nutritive value, and N response of seven annual forage species and one grass–legume biculture, no-till planted into spring-terminated alfalfa. Forages were planted in late May at Rosemount, MN, in 2014 and 2015 and at Waseca, MN, in 2015 with split-plot factors of three N fertilizer rates (0, 56, and 112 kg N ha–1) and were harvested on approximately 30-d intervals. When successfully established, teff [Eragrotis tef (Zuccagni) ‘Summer Lovegrass’] and sudangrass [Sorghum bicolor (L.) subsp. drummondii (Nees ex Steud.) ‘PCS 3010’] were among the highest-yielding species, with yields ranging from 4.2 to 9.9 Mg DM ha–1 and 6.8 to 8.9 Mg DM ha–1, respectively. Fertilizer N increased yields of all species at Rosemount in 2014; however, N needs were met by terminated alfalfa at both locations in 2015. Weed biomass increased with added fertilizer N in site-years when weeds were present. Nitrogen fertilization improved forage nutritive value through decreased neutral detergent fiber concentration and increased crude protein concentration and neutral detergent fiber digestibility (48-h in-vitro) in all site-years. However, N fertilization had no effect on economic net return in 2 of 3 site-years. Annual ryegrass [Lolium multifl orum (Lam.) ‘Jumbo’] most consistently resulted in the greatest net return. No-till planting annual forages into terminated alfalfa can provide forage to off set losses and utilize alfalfa N in situations of alfalfa winter-kill.
Bibliographical noteFunding Information:
This project was partially funded by the University of Minnesota Agricultural Experiment Station. We appreciate the field support and technical contributions of Eric Ristau and Joshua Larson, and all who assisted with the forage sampling, processing, and analyses for this study.
© 2017 American Society of Agronomy.
Copyright 2017 Elsevier B.V., All rights reserved.