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  1. Vol. 28 No. 2, p. 354-358
     
    Received: May 11, 1987
    Published: Mar, 1988


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doi:10.2135/cropsci1988.0011183X002800020036x

Prediction of Percentage Leaf in Stratified Canopies of Alfalfa with Near Infrared Reflectance Spectroscopy

  1. N. S. Hill ,
  2. J. C. Petersen,
  3. J. A. Stuedemann and
  4. F. E. Barton
  1. U SDA-ARS, Southern Piedmont Conserv. Ctr., Watkinsville, GA 30677;
    P lant Structures Unit, USDA-ARS, Russell Res. Ctr., Athens, GA 30613.

Abstract

Abstract

Because digestibility is maintained with leaf but declines with stem age, study of the plant-animal interface may yield information regarding grazing management options for legume based pastures. Current methods used to analyze esophageal samples for dietary components are time consuming and inherent with human error. The objectives of this study were to determine if percentage leaf could be predicted by near infrared reflectance spectroscopy (NIRS) and if predictions were affected by cultivar differences or addition of saliva to artificially mixed samples of alfalfa (Medicago sativa L.). Two genetically diverse cultivars, ‘Apollo’ and ‘Florida-77’, were hand-clipped from field plots at the 1/10 bloom stage throughout the 1986 growing season. Harvested plants were separated into top, middle, and bottom strata and the leaves and stems separated. Bovine (Bos taurus) saliva was added to half of each of the leaf and stem fractions, masticated with a mortar and pestle, and the samples freeze-dried and ground. Artificial sample sets varying in percent leaf and stem were used to establish NIRS calibration equations. Coefficients of multiple determinations for calibration (R2) and coefficients of determination for prediction (r2) were 0.96 and 0.93 or better, respectively, and standard errors of calibration and prediction were 5.60 and 7.41 or lower, respectively, among successful calibration equations. Calibration of NIRS with Fla-77 samples failed when used to predict the Apollo set. We conclude that NIRS is a rapid and accurate method to determine percentage leaf in alfalfa, and solids in saliva had no effect on light reflectance at the selected wavelengths.

Contribution from the Dep. of Agronomy, Univ. of Georgia; USDA-ARS Southern Piedmont Conserv. Ctr.; and USDA-ARS Russell Res. Ctr.

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