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Agronomy Journal Abstract -

A Power Parabola for an Asymmetrical Response


This article in AJ

  1. Vol. 69 No. 1, p. 124-125
    Received: May 14, 1976

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  1. Carol J. Adams and
  2. F. J. Hills2



As plant density increases, crop yield often increases, reaches a plateau, then decreases at a different rate. It is difficult to find a simple equation that will adequately describe this situation. A FORTRAN IV program is presented which can be used to fit a parabola to such an asymmetrical response by the transformation of abscissa and ordinate values to calculated powers, i.e. Yw = a + bXz + c(Xz)2. The procedure is illustrated with the response of sugar beet (Beta vulgaris L.) root yield to plant density in field plots and resulted in a power parabola of excellent fit (R2 = 0.955).

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