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grains, and other agricultural crops. 
analyses reported here are: 
The specific objectives of the 
1. To examine the effects of cultural and environmental factors 
on the spectral response of spring wheat. 
2. To determine the relationship of agronomic variables such as 
biomass and leaf area index to multispectral reflectance of 
spring wheat. 
Experimental Approach 
The data used for these analyses were collected using a truck- 
mounted spectrometer during the first two years of the LACIE field 
research program at the agriculture experiment station at Williston, 
North Dakota. Measurements were made at approximately weekly intervals 
of the bidirectional reflectance factor and agronomic characteristics 
of 32 plots of spring wheat (Robinson et al., 1978). The design of 
the experiment was a 2" factorial with two replications. The factors 
and levels were: 
Soil Moisture: (1) wheat during previous year, (2) fallow during 
previous year. 
Planting Date: (1) early, (2) late. 
Cultivar: (1) standard height, (2) semi-dwarf. 
Nitrogen Fertilization: (1) None, (2) 34 kg/ha. 
The tactors and levels were selected to represent regional agri- 
cultural practices that affect the growth, development, and yield of 
spring wheat. The treatments resulted in a relatively wide range of 
types of wheat canopies, differing in maturity, biomass, and percent 
soil cover at any one time and over the season. 
In addition to reflectance, the following agronomic variables 
were measured: maturity stage, height, percent soil cover, leaf area 
index, percent green leaves, fresh and dry biomass, and plant water 
content (difference between fresh and dry biomass). Vertical and 
oblique photographs were taken of each plot on each measurement date. 
After processing, graphs of the spectral data were examined to 
verify data quality and qualitatively assess the information contained 
in the spectra. Correlation and regression analyses were used to relate 
biological and physical variables describing the canopies to spectral 
response. 
Since the application of remotely sensed spectral measurements 
will be with multispectral scanner systems which measure the spectral 
response in selected wavelength bands, the statistical analyses were