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This article in AJ

  1. Vol. 85 No. 1, p. 140-146

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Development of Soybean Fresh and Dry Weight Relationships for Real Time Model Calibration

  1. A. Kenig,
  2. J.W. Mishoe *,
  3. K.J. Boote,
  4. P.W. Cook,
  5. D.C. Reicosky,
  6. W.T. Pettigrew and
  7. H.F. Hodges
  1. A rava Exp. Stn., Mobile Post Hevel Eilot 88820, Israel
    A gricultural Engineering Dept
    A gronomy Dep., Univ. of Florida, Gainesville, FL 32611
    M athematical Statistician, Survey Res. Branch, Estimates Res. Section, USDA-NASS, Washington, DC 20251
    U SDA-ARS, North Central Conserv. Res. Lab., Morris, MN 56267
    U SDA-ARS, Univ. of Illinois, Urbana, IL 61801
    A gronomy Dep., Univ. of Mississippi, Mississippi State, MS 39762



Measurements of dry weight and crop phenology are normally used to validate comprehensive growth models. To reduce this requirement in applications such as large area yield forecasting, the present research was conducted to study the change of dry matter concentration (ratio of dry weight to fresh weight) of the vegetative and reproductive plant components of soybean (Glycine max (L.) Merr.]. The paper evaluates the usefulness of simple statistical equations that relate dry matter concentration to developmental stages for the specific purpose of growth model calibration. During the 1984 through 1985 seasons, five cultivars of soybean were grown in five locations throughout the soybean producing regions of the U.S. Soil type, planting date, plant population, and irrigation management varied from site to site. Plant samples were taken at 1- to 2-wk intervals during the growing season for fresh weight and dry weight of vegetative parts and pods, and counts of reproductive sites. In most of the field locations, dry matter concentration of different soybean parts was found to follow a predictable pattern. The pattern was explained for most locations by a simple relation of developmental stage and vegetative dry matter concentration, using data collected until the beginning of pod fill. A second model explained the course of pod dry matter concentration over developmental stage, using data collected after the beginning of seed growth. Insignificant differences among regression lines of extreme locations suggest that the course of dry matter concentration may be of an inherent nature, with minor impact due to differences of cultivar, or weather. The equations developed in this paper to estimate dry weight data will reduce the effort of calibrating and/or validating soybean comprehensive growth models by requiring only the collection of fresh weight samples at known phenological events.

Contribution from the Univ. of Florida, Inst. of Food and Agric. Sciences, Florida Agric. Exp. Stn. Journal Series no. R01148. The work was conducted under a cooperative agreement no. 58-319T-10109X between the USDA/ NASS and the Univ. of Florida.

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