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This article in AJ

  1. Vol. 64 No. 5, p. 635-639
     
    Received: Jan 13, 1972
    Published: Sept, 1972


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doi:10.2134/agronj1972.00021962006400050026x

Emergence Force of Forage Seedlings1

  1. E. H. Jensen,
  2. James R. Frelich and
  3. R. O. Gifford2

Abstract

Abstract

The experiments were conducted to quantitatively determine the relative force exerted by germinating forage seedlings. Information obtained could be used for the selection of forage species most likely to emerge through soil crusts.

An apparatus was used that employed a force transducer to measure the relative force exerted during seedling emergence. A continuous record of the vertical force was observed for each seedling. The resulting curve reflected the relative force a seedling exerted at a particular time of emergence after germination.

The emergence force exerted by a seedling differed significantly among alfalfa (‘Medicago sativa’ L.), strawberry clover (Trifolium fragiferum L. ‘Salina’), alsike clover (Trifolium hybridium L.), and narrow-leaf birdsfoot trefoil (Lotus tennis Wald. et. Kit.) and was positively correlated with seed weight. Alfalfa exhibited a significantly higher mean weekly emergence force, while narrowleaf birdsfoot trefoil seedlings exerted a significantly lower mean weekly emergence force than the other species tested. Curves generally indicate that force increased very rapidly for legumes 24 to 48 hours after transplanting with a gradual decrease thereafter. The magnitude of force exerted by tall wheatgrass (Agropyron elongatum Host) and alfalfa seedlings was not significantly decreased until –5.0 bars of osmotic potential (O.P.) was imposed. A decrease in O.P., however, significantly increased the time required to reach a maximum force by alfalfa but not by tall wheatgrass. Force curves of tall wheatgrass indicated that 5 to 6 days were required to reach a maximum force, compared to 1 to 2 days for legumes. Sodium adsorption ratios did not affect the emergence force of alfalfa seedlings.

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