Z CIRCULAR 558, U. S. DEPARTMENT OF AGRICULTURE 
seeded alone, most of the seed was sown as part of a grass mixture 
planted to alfalfa or as part of a sweetclover-grass mixture. Reports 
from field agronomists and farmers who have previously handled 
unprocessed seed agree that in addition to facilitating planting, proc- 
essing promotes more uniform stands and reduces the labor required 
to make the seedings. 
METHODS 
Seed of bluebunch wheatgrass (Agropyron spicatum), blue wild-rye 
(Elymus glaucus), Canada wild-rye (. canadensis), Siberian wild-rye 
(EZ. sibericus), tall oatgrass (Arrhenatherum elatius), bulbous barley 
(Hordeum bulbosum), squirreltail (Sitanion hystrix), alfileria (Hrodium 
cicutarium), and virgins-bower (Clematis ligusticifolia) was used in 
the studies at the Pullman nursery. The seed of bluebunch wheat- 
grass, blue and Siberian wild-rye, tall oatgrass, and squirreltail were 
machine threshed; the other seed had been threshed by hand. At- 
tempts to remove the awns from grass seed, the tails of the carpels 
from alfileria, and the styles from virgins-bower by rubbing, burning 
with a torch, or using small bur mills, were slow and expensive and 
damaged a high percentage of the seed. One lot of Canada wild-rye 
was successfully deawned at the nursery in the normal threshing 
operation by speeding up the cylinder, using three rows of concave 
teeth set to thresh close, adjusting the sieves, and removing two- 
thirds of the fan blades to reduce the air blast. However, the grass 
was harvested with a binder at an early stage of maturity and was so 
cured in the shock as to obtain a desirable moisture content at the 
time of threshing. Under conditions of large-scale operations atten- 
tion to such factors is hardly practical. One commercial seed grower 
in the Northwest had used the hammer mill to break up the multiple 
florets common in threshed seed of crested wheatgrass (Agropyron 
cristatum). These experiences suggested the use of the mill for de- 
awning seed.® : 
Two types of medium-sized hammer mill were used. Most of the 
work was done with the swinging-hammer type, and for comparison 
a solid-hammer type was used in deawning two typical species. The 
detailed specifications for each mill are given in table 1. These mills 
represent the types and sizes most commonly used on farms in the 
Pacific Northwest. Other mills were available but were not equipped 
with screens suitable for use in these studies. 
TaBLE 1.—Specifications for two typical medium-sized hammer mills used for 
deawning grass seed 
. . Normal 
- Siz Diame T Nae 
Type of hammer F corps S 706 of Bas Hammers ee srinding 
speed 
Revolutions 
Inches Inches Inches Number Number | per minute 
Spy rd ee pee 9 by 13144] 113 by 44 26 2 48 2, 250 
SOlid== ee eee ee eee 1l by 14 14 by 36 22 30 30 2, 250 
1 An additional 44-inch screen 13 by 28 inches is spot-welded in the hood of this machine. 
3 This method has also been reported in the following: WEBER, G. L. A METHOD OF PREPARING SOME 
NATIVE GRASS SEEDS FOR HANDLING AND SEEDING. Amer. Soc. Agron. Jour. 31:729-733. 1939. 
