a2 CIRCULAR 925, U. S. DEPARTMENT OF AGRICULTURE 
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1935 1937 1939 1941 1943 1945 1947 
Figure 14.—Average annual herbage production of winterfat and calculated trend 
of production in 6 lightly, 7 moderately, and 7 heavily grazed range pastures, 
1935-47. 
HERBAGE PRODUCTION CPOUNDS PER ACRE) 
Yield of shadscale, the most abundant species, showed upward trends 
under all intensities of grazing. The trends were slightly greater with 
moderate, and considerably greater with light grazing than with heavy. 
This was probably because more of the seed was eaten on the heavily 
grazed range, thus decreasing the amount of reproduction. Average 
utilization under light, moderate, and heavy grazing was 20, 21, and 
28 percent; plant vigor was therefore probably not diminished at any 
intensity. 
Indian ricegrass showed little trend in relation to the different degrees 
of grazing. In these subtypes it makes up only a small proportion of 
the vegetation and was overgrazed at least in some years in all pastures. 
Average utilization under light, moderate, and heavy grazing was 65, 
76, and 88 percent. The trend in production was downward for all 
three degrees of use to 1943. In the dry years of 1942 and 1943 yields, 
although generally low, were slightly higher under light and moderate 
use than under heavy. The rate of recovery after 1943 was somewhat 
more rapid under the first two intensities. 
Galleta yields were greater in all years under light and moderate 
intensity than under heavy . The three intensities ‘showed respective 
downward trends of 27, 14, and 35 percent. The differences between 
trends were not statistically significant. Average utilization was 20, 
49, and 67 percent under light, moderate, and heavy grazing. Only 
in the years of 1939 and 1941, when favorable summer rainfall occurred 
and production increased, did differences ascribable to grazing treat- 
ment emerge. In both of these years production increased more with 
light and moderate grazing than with heavy grazing. 
Production of sand dropseed also showed slight downward trends 
for all grazing treatments, although this species was utilized only 9, 
