Full TGIF Record # 71210
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Web URL(s):http://www.tandfonline.com/doi/pdf/10.1080/01904169809365563
    Last checked: 10/13/2015
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Author(s):Taylor, Shannon L.; Raun, WIlliam R.; Solie, John B.; Johnson, Gordon V.; Stone, Marvin L.; Whitney, Richard W.
Author Affiliation:Taylor, Raun, and Johnson: Department of Agronomy, Oklahoma State University, Stillwater, OK; Solie, Stone, and Whitney: Department of Biosystems and Agricultural Engineering, Oklahome State University, Stillwater, OK
Title:Use of spectral radiance for correcting nitrogen deficiencies and estimating soil test variability in an established bermudagrass pasture
Source:Journal of Plant Nutrition. Vol. 21, No. 11, 1998, p. 2287-2302.
# of Pages:16
Publishing Information:New York: Marcel Dekker, Inc.
Keywords:TIC Keywords: Spectral radiance; Nitrogen; Nutrient deficiency; Soil testing; Fertilization rates; Measurement; Cynodon dactylon; Biomass; Forage; Nitrogen fertilization; Fertilization; Soil types; Chemical properties of soil; Soil pH; Fertilization timing; Nitrogen uptake; Clipping weight
Cultivar Names:Midland
Abstract/Contents:"The use of variable rate technology has become increasingly popular for applying plant nutrient elements. The most widely used method for determining variable fertilizer rates is presently based on soil testing and yield mapping. Three field studies (Burneyville 1995, Burneyville 1996, and Ardmore 1996) were initiated in established Midland bermudagrass [Cynodon dacrylon [dactylon] (L) Pers.] pastures to determine the relationship between spectral radiance at specific wavelengths with forage nitrogen (N) removal and biomass, and to determine field variability of soil test parameters. Variable N (applied to 1.5 x 2.4m subplots within 2.4 x 45.7m main plots), fixed N and check treatments were evaluated at each location. Spectral radiance readings were taken in the red (671+/-6nm), green (570+/-6nm), and near infrared (NIR) (780+/-6nm) wavelengths. The normalized difference vegetation index (NDVI) was calculated as NIR-red/NIR+red. Variable N rates were applied based on NDVI. The highest fixed variable N rate was set at 224, 336, and 672 kg N ha⁻1 for Burneyville, 1995, 1996, and Ardmore, 1996, respectively. At Burneyville, soil samples were collected in all variable rate plots (1.5 x 2.4m) and analyzed for various soil test characteristics. NDVI, red, green, and NIR spectral radiance readings were correlated with bermudagrass forage N removal and yield. Correlation of forage yield and N removal with red, NIR, and NDVI were best with maximum forage production, however, when forage production levels with low correlation increased dramatically for the red wavelength compared with NIR and NDVI. Forage yield and forage N removal in variable rate treatments increased when compared to the check while being equal to the half-fixed and fixed rates where higher N rates were applied. Also, variability about the mean in variable rate plots was significantly lower than half-fixed and fixed rates which supports adjusting N rates based on indirect NDVI measurements. Variable N rate plots reduced fertilizer inputs by 60% and produced the same yield as fixed rate plots, while fixed and half-fixed rates did not increase N content in the forage over that of the variable rate treatment. Soil sample data collected from small consecutive plots (<4 m²) was extremely variable indicating that intense sampling would be needed if variable fertilizer application were to be based on soil test results."
ASA/CSSA/SSSA Citation (Crop Science-Like - may be incomplete):
Taylor, S. L., W. R. Raun, J. B. Solie, G. V. Johnson, M. L. Stone, and R. W. Whitney. 1998. Use of spectral radiance for correcting nitrogen deficiencies and estimating soil test variability in an established bermudagrass pasture. J. Plant Nutr. 21(11):p. 2287-2302.
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    Last checked: 10/13/2015
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