in Fig. 2. Biophysical measurements (including fresh and dry
biomass, plant height, and LAI) were observed weekly.
The biomass and VWC were measured as the sum of leaves,
stem, and pods by destructive sampling. Total LAI was measured
using a LAI-3100 (LI-COR, Lincoln, NE), which is a direct
method for estimating total LAI. This instrument operates
differently than the device used with rice in 2007. However, an
earlier study by Welles [20] showed that observations made by
the direct (LAI-3100) and indirect (LAI-2000) methods compared
well with each other. Measurement of the soil moisture
within the top 0.05 m was performed using a portable probe
(Echo-5 TE probe, Decagon Device, Inc.). NDVI data were not
available for the soybean experiment. Crop row orientation was
parallel to the azimuth angle of the antenna.