Purdue Agronomy Farm Corn Nitrogen (781802)
Nitrogen fertilization is one of the primary factors responsible for the
increased yields in the United States in the past 15 years. Four levels of
fertilization, 0, 67, 134, and 202 kg/hectare, providing a range from
distinctly deficient to abundant have been selected from a long term
fertilization experiment. The specific objectives of the experiment were to
(1) determine the threshold of spectral detection of nitrogen deficiency
and (2) determine kind and magnitude of changes in reflectance and
thermal response as a function of level of nitrogen nutrition. Three
replications were used. Measurements were made at approximately 10
day intervals throughout the growing season with the Exotech 20C
spectroradiometer over the 0.4 to 2.4 um wavelength range and the
Exotech 100 Landsat band radiometer. Radiant temperature of the
canopy was also measured.
Agronomic characterizations of the canopies included: leaf area index,
biomass, percent soil cover, height, leaf nitrogen, chlorophyll
concentration, development stage and grain yield. Vertical and oblique
photographs were also taken of the canopies.