Purdue Agronomy Farm Soybean Row Direction (791810)
The objective of the experiment is to determine the effect of rows
and row direction, variables in the area of cultural practices, on the
reflective response of a soybean canopy as a function of azimuth and
zenith sun angles. The design of the experiment involved 11 plots.
One plot was planted in east-west and north-south rows 25 cm wide
to obtain, at later growth stages, a canopy with negligible row effects.
A second plot was bare soil, providing an opportunity to monitor the
reflectance of the soil background of the soybean plots. The
remaining nine plots were planted in soybeans with 76 cm wide
rows with the following azimuthal directions: 90-270, 105-285, 120-
300, 135-315, 150-330, 165-345, 180-360, 210-030, and 240-060
degrees. The row directions were selected to maximize the
probability of obtaining data during the morning hours when cloud
conditions are more favorable for data collection than in the
afternoon. Reflectance data were acquired at 15 minute intervals
throughout the day on three days, representing three canopy growth
stages.
Data analysis involves mathematically modeling the effect of
combinations of sun azimuth and sun zenith angles on the reflectance
from a row crop of soybeans. The experiment design permits the
effect of sun angles to be analyzed independently.