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In the fall of 1993, variable N rates using an inverse N-rate, NDVI scale
were attempted at Miller-2. Using this approach, N-rates were cut in half
with no differences in grain yield compared to fixed rates. Grain N uptake
levels using VRT across a 70 meter transect were less variable when compared
to the fixed rates (below) .
The initial algorithms used to spatially treat N deficiencies in wheat
and bermudagrass employed an inverse N Rate-NDVI scale. Later, critical
NDVI levels were established (both min and max) resulting in a plateau-linear-plateau
function.
 In
the summer of 1994, John Ringer and Shannon Osborne collected sensor readings
and later applied variable N fertilizer rates based on an initial bermudagrass
algorithm developed by TEAM-VRT.
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1994
