T
U.S.S.R. SPRING
WHEAT REGION
20
1
26
CROP REGION
18 - NORTHWEST URALS
19 - SOUTHERN URALS \ 1
20 - NORTHEASTERN URALS
21 - WESTERN KAZAKHSTAN
22 KUSTANAY OBLAST
Figure 14.— Percent deviation from normal in moisture supply in
Soviet spring wheat regions.
season seriously depleted soil moisture
supply throughout the southern portions
of the Soviet spring wheat area. Note
that the northern regions had normal to
above-normal moisture. In addition, the
April temperature was nearly 4°C above
normal, and the average precipitation
somewhat below normal in the drought-
affected regions.
An investigation of the Landsat data
and the yield model response at sub-
regional levels indicated that the drought
conditions were clearly observable in the
Landsat data and that the yield models
accurately responded by reducing yield
estimates in the affected regions. Note
on figure 15, the severe reductions in
yield in the affected regions - in many
cases 50% below normal. LACIE yield
models reduced the yield prospects
nearly 2 quintals per hectare in the
drought-affected regions in response to
the hot, dry April. The continuing
drought reduced the yield nearly 2 more
quintals below the 11.5 quintal normal.
In figure 16, it can be seen that these
drought conditions were also quite eviden
in the Landsat data. Certain Landsat
radiometric measurements known to be
related to crop vigor and called "green
index numbers" (12), indicated that the
crop in the shaded areas was severely
stressed. Note, however, that in the
northern regions LACIE was forecasting
above-normal yields. Figure 17 illus-
trates the drought effects visible in
Landsat imagery from the affected area.
The two right-hand full-frame images,
collected on July 4, 1977, were from a
normal moisture area (Omsk oblast, at the
top) and from a moisture-stressed area
(Kokchetav oblast, at the bottom). The
degree of darkness (redness) in the image
is an indicator of crop vigor. When the
1977 image for the Kokchetav segment is
compared to the image on the left
collected from the same oblast the
previous year, a dramatic decrease in
crop vigor can be seen. Now one problem
remained: How much overall impact on
spring wheat production would these