GEAZING EANGES IN" SOUTHEEN AEIZONA. 21 



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 1,213 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, if 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,^ 1905,^ 1907,^ 1908,^ 1912,- 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 



1 See Bureau of Plant Industry Bulletin 177, p. 19. 



- Totals obtained from averages of all spring and summer collections daring these years 

 on file in the Office of Farm Management. 



2 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. 



