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 yet 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 hay-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 ITI. 
TABLE III.—Comparison of the total production of herbage per acre, as calcu- 
lated from quadrat measurements, with the actual amounts of hay obtained 
from measured areas embracing or beside the quadrats, on the Santa Rita 
Range Reserve, Ariz. 
Data from quadrats. | Percentage 
| of total 
| Pounds of | production 
Location of cutting. Total hay from |” obtained 
Quadrat | herbage in| ‘lacre. by hay- 
No. pounds cutting 
per acre. operations. 
Plat B, first cutting, near Proctor’s camp (1.4 acreés)....- 26 1,372 1,037 74.8 
Plat C, second cutting, near old haystack (1 acre)........ 27 1677 1921 76.9 
Rielasintl G1Bs ees ee see ae i fosd sac beeen tee ae 29 823 504 67.3 
BWelix:in 1912s ae ae a ene ode See odes eee ee eee 18 948 750 79.1 
Relic inode A Ski Mame Cth! MLA. eA ane { re \ 876 794 90.6 
iPlowediacromeantvate: sae prema astae cnn Oe eee eee 16 | 1,609 750 40.6 
A VOTAGES scien be LEE eee eke. A eae 1,044 734 71.5 
1 The area was mowed the previous season, but no data were obtained.. The collection represents the 
same growth as the hay cut, however, and they are therefore comparable. 
