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Nitrogen Fertilization Rates Influence Stockpiled Tall Fescue Forage through Winter
Author(s) -
Kallenbach Robert,
Roberts Craig,
Lory John,
Hamilton Stacey
Publication year - 2017
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci2016.02.0097
Subject(s) - forage , human fertilization , red clover , biology , agronomy , grazing , dry matter , zoology , fodder
Tall fescue [ Lolium arundinaceum (Schreb.) Darbyish.] can be autumn stockpiled to extend the grazing season. The objectives of this study were to determine (i) optimum mid‐August N fertilization rate for stockpiled yield with or without red clover ( Trifolium pratense L.), (ii) if mid‐August N applications affect the persistence of red clover in a mixed sward, (iii) how N fertilization rates affect total ergot alkaloids (TEA) in November, and (iv) if N fertilization rates and harvest months affect nutritive value through winter. At the University of Missouri Forage Systems Research Center near Linneus, MO, five N fertilization rates were applied in mid‐August and forage was harvested the following November through March. Dry matter yield, crude protein (CP), and in vitro true digestibility (IVTD) were determined for each sampling date. Each November, TEA were measured from tall fescue‐only plots. Red clover densities were determined each June. Stockpiled yields increased with increasing N fertilization rates up to 168 kg N ha −1 . Red clover neither impaired nor improved stockpiled forage yield. Red clover densities decreased linearly as N fertilization rate increased the previous August. Sward type affected nutritive value minimally. Losses in CP and IVTD through winter averaged 20 and 60 g kg −1 , respectively, over the 4 yr. Application of 56 kg N ha −1 provided forage with CP concentrations that would support nonlactating beef cows. Fertilization rates of ≥112 kg N ha −1 resulted in November TEA concentrations that are toxic to grazing livestock. For optimum stockpiled forage yields, forage should be fertilized with <112 kg N ha −1 and grazed before January.

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