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