GRAZING RANGES IN SOUTHERN ARIZONA. mat 
Following is an attempt to estimate the total production on the 
fenced area. As computed from recent quadrat collections, the 
crowfoot-grama association produces about 1,045 pounds of summer 
forage and 178 pounds of spring forage per year, a total of 1,223 
pounds per acre. The needle-grass association produces 1,243 pounds 
of summer growth and fully as much spring growth as the crowfoot- 
grama area, a total of 1,421 pounds at least. The productivity indi- 
cated by the single collection for the black-grama area, 1,217 pounds, 
is certainly more than an average, and the total annual production 
for the area is certainly not over 1,000 pounds per acre. The average 
production, as computed from the four spring and two summer col- 
lections from the six-weeks-grass area, is 871 pounds per acre. The 
remainder of the area does not produce over 400 pounds of forage 
per acre, 1f that much. A weighted average of the above figures, 
using round numbers, is as follows: Thirty-one sections of the first- 
named association at 1,200 pounds, 10 sections of the second at 1.400 
pounds, 7 sections of the third at 1,000 pounds, 6 sections of the 
fourth at 800 pounds, and 4 sections of the last at 400 pounds. This 
accounts for the whole of the fenced area and gives an average pro- 
duction of 1,110 pounds of forage per acre. 
An average of the total production of forage, as shown by the col- 
lections made in 1903, 1904,1 1905, 1907, 19081 1912.2 and 1914, 
shows an average production of 1,160 pounds per acre. Thus two 
methods of computation reach practically the same result, which, in 
round numbers, may be taken at 1,100 pounds per acre as represent- 
ing about normal productivity for this region. 
If the figure representing average summer production on the 
crowfoot-grama area (1,045 pounds per acre), this being the area 
where all the hay cutting has been done, be compared with the 
average hay production (640 pounds per acre),? it is seen that the 
haying methods get roughly 60 per cent of the annual growth. 
Stock will gather a crop more closely than the mower, but not so 
closely as the quadrat collections were made. They probably do get 
from 75 to 80 per cent of the crop produced each season on the open 
range, and this includes the spring as well as the summer growth 
wherever the range is stocked to the limit. 
It is equally true that even as close collecting as the haying opera- 
tions make, at a time no more unfavorable to the plants than when 
the hay is cut, ultimately results in a marked reduction of the total 
amount of feed produced. (See Table V for effect of repeated 
1See Bureau of Plant Industry Bulletin 177, p. 19. 
+ Totals obtained from averages of all spring and summer collections during these years 
on file in the Office of Farm Management. 
3 See Table IV, showing average weight of hay per acre. Table III gives actual com- 
parisons on a few selected areas. The average result is probably too great. 
