20 



BULLETIN 367, U. S. DEPARTMENT OF AGRICULTURE. 



one collection) of the total vegetation on the area. In every case 

 there was considerable perennial grass, never more than partly 

 grown at the time of collection, thus increasing the apparent pro- 

 portion of the spring growth. Estimates of the average productivity 

 of the black-grama and six-weeks-grass areas, as made from the 

 quadrat collections, would not be comparable with the results given 

 in the table, mainly because neither of those areas has jet reached a 

 state of normal productivity, and also because recent collections from 

 these areas are not numerous enough to give fair averages. The only 

 fall collection made recently in the black-grama area plainly gives 

 too high a total production (1,210 pounds per acre) for an average 

 annual productivity of that area. Another difficulty was encoun- 

 tered in making this collection, which applies to collections of wire 

 grama also. These grasses do not die completely back to the ground 

 in the winter ; hence, it becomes very difficult to collect the growth of 

 a single year, being absolutely sure that none of the growth of pre- 

 vious seasons has been included. 



It will be very evident to the reader that the haj^-cutting records 

 are not directly comparable with the collections made on the quad- 

 rats. On the mowed areas the herbage obtained is only that part 

 which can be cut by a mowing machine and picked up by a rake. On 

 the quadrats every bit of vegetation above the surface of the ground 

 was very carefully collected and weighed to an accuracy of 0.2 gram, 

 a limit of accuracy which reduces to 1 pound of dried feed per acre. 

 A number of collections were made on areas before they were mown 

 and others on undisturbed areas besides the mown ones. While the 

 number of these comparisons is not large enough to give a ratio 

 which may be considered exact, the comparisons are at least quite 

 suggestive. They are mostly easily seen in Table III. 



Table III. — Comparison of the total production of herbage per acre, as calcu- 

 lated from, quadrat measurements, tvith the actual amounts of hay obtained 

 from measured areas embracing or beside the quadrats, on the Santa Rita 

 Range Reserve, Ariz. 





Data from quadrats. 



Pounds of 



hay from 



1 acre. 



Percentage 

 of total 



Location of cutting. 



Quadrat 

 No. 



Total 



herbage in 



pounds 



per acre. 



production 

 obtained 

 by hay- 

 cutting 



operations. 



Plat B, first cutting, near Proctor's camp (1.4 acres) 



Plat C, second cutting, near old haj^stack (1 acre) 



Ruelas in 1913. . .'. 



26 

 27 

 29 

 18 

 f 48 

 \ 49 

 16 



1,372 



1677 

 823 

 948 



} 876 



1,609 



1,037 



1521 



554 



750 



794 



750 



74.8 

 76.9 

 67.3 



Felix in 1912 



79.1 



Felix in 1914 



90 6 





40.6 







Average 





1,044 



734 



71.5 









1 The area was mowed the previous season, but no data were obtained, 

 same growth as the hay cut, however, and they are therefore comparable. 



The collection represents the 



