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This article in AJ

  1. Vol. 79 No. 2, p. 254-259
     
    Received: Sept 3, 1985


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doi:10.2134/agronj1987.00021962007900020016x

Greenness-Leaf Area Index Relationships of Seven Row Crops1

  1. M. S. Redelfs,
  2. L. R. Stone,
  3. E. T. Kanemasu and
  4. M. B. Kirkham2

Abstract

Abstract

Remote sensing technology has potential for nondestructive estimation of green leaf area index (LAI). We applied the greenness transformation to ground-based reflectance data taken over seven crops [sweet and field corn, Zea mays L.; grain sorghum, Sorghum bicolor (L.) Moench; pearl millet, Pennisetum americanum (L.) Leeke; pinto bean, Phaseolus vulgaris L.; soybean, Glycine mar (L.) Merr.; and sunflower, Helianthus annuus L.] grown on Eudora silt loam soil (coarse-silty, mixed, mesic Fluventic Hapludoll) to determine reflectance-LAI relationships, and to see if those relationships were crop specific or could be applied more generally to several crops. Spectral reflectance data were collected with a radiometer equipped with four wavelength bands that simulated the Landsat multispectral scanner bands. The coefficients for brightness and greenness were calculated by using reflectance data and published calculation procedures. Greenness coefficients for the reflectance data for all crops were very similar. Models were developed that related greenness (calculated by using the individual crop greenness coefficients or the coefficients developed from combined data of all crops) and field estimates of green LAI. All models were significant (P<0.0001) and linear, with the regression coefficients equal to what we termed the crop factor. Intercepts were not significantly different from zero (P>0.05). The combined greenness coefficients were not significantly different than individual crop coefficients in relating greenness to field-estimated LAI. The crops were grouped into grass or broadleaf to determine general crop factors. It made no significant difference whether the individual crop factor or the combined crop factor (for grass, 0.197; for broadleaf, 0.117) was used in developing the greenness-estimated LA1 that was related to field-estimated LAI. This study illustrated that the greenness coefficients developed for each of seven row crops were very similar and the regression coefficients from the linear relationship between LA1 and reflectance greenness were very similar within the grass crops and within the broadleaf crops.

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