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Agronomy Journal Abstract - Crop Economics, Production & Management

Nonstructural Carbohydrate Concentration during Field Wilting of PM- and AM-Cut Alfalfa


This article in AJ

  1. Vol. 104 No. 3, p. 649-660
    Received: Nov 16, 2011

    * Corresponding author(s): gaetan.tremblay@agr.gc.ca
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  1. Chantale Morina,
  2. Gaëtan F. Tremblay *b,
  3. Gilles Bélangerb,
  4. Annick Bertrandb,
  5. Yves Castonguayb,
  6. Raynald Drapeauc,
  7. Réal Michaudb,
  8. Robert Berthiaumed and
  9. Guy Allarda
  1. a Faculté des Sciences de l'Agriculture et de l'Alimentation, Université Laval, 2425 rue de l'Agriculture, Québec, QC, Canada G1V 0A6
    b Agriculture and Agri-Food Canada, Soils and Crops Research and Development Centre, 2560 Hochelaga Blvd, Québec, QC, Canada G1V 2J3
    c Agriculture and Agri-Food Canada, Research Farm, 1468 St-Cyrille Street, Normandin, QC, Canada G8M 4K3
    d Agriculture and Agri-Food Canada, Dairy and Swine Research and Development Centre, 2000 College Street, Sherbrooke, QC, Canada J1M 0C8


Alfalfa (Medicago sativa L.) cut in the late afternoon has a greater nonstructural carbohydrate (NSC) concentration than AM-cut alfalfa but this difference might not be maintained during wilting. We monitored NSC concentration of PM- and AM-cut alfalfa during wilting in narrow and wide swaths. Field-grown alfalfa was cut either at 1800 h (PM) on days without rain (Day 0) or at 0800 h (AM) the following morning (Day 1) in seven growth cycles over 3 yr. Samples taken during wilting were analyzed for NSC (soluble carbohydrates + starch). At cutting, PM-cut alfalfa had consistently greater NSC concentration [+6 to 54 g kg1 of dry matter (DM)] than AM-cut alfalfa. The NSC concentration decreased during wilting at rates that depended on growth cycles (0.2–3.5 g kg1 DM h1 on Day 1) but this decline was similar for AM- and PM-cut alfalfa. When cut alfalfa reached 350 g DM kg1 fresh matter (FM) on Day 1, NSC concentration was greater for PM- than for AM-cut alfalfa (average of 15 with a range of 4–37 g kg1 DM) and greater for the wide than narrow swaths (average of 7 with a range of 1–11 g kg1 DM). Photosynthesis continued for 3 h on the morning of AM cutting for both PM- and AM-cut alfalfa until DM concentration reached approximately 350 g DM kg1 FM. The combination of late PM-cutting and wilting in wide swaths can be used to increase the NSC concentration of wilted alfalfa.

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