60 BULLETIN 981, U. S. DEPARTMENT OF AGRICULTURE. 
ghum plants can be easily distinguished by their broader leaves and 
heavier stems. 
Johnson grass does not cross-pollinate as freely with Sudan grass as 
the sorghums do, but natural crossing does occur when the two grasses 
grow in mixtures or in adjoining rows. It is important, therefore, 
to see that no Johnson grass is allowed to bloom in the Sudan grass 
field, because of the possibility of hybridization. 
ROGUING THE FIELDS. 
If pure seed is to be produced, every grower must remove from his 
Sudan grass field all sorghum and Johnson grass, and also hybrids 
between these crops and Sudan grass. Sorghum plants and sorghum- 
Sudan grass hybrids are coarser and usually taller than the Sudan 
grass. Some growers have found that the most effective way of locat- 
ing these rogues is to ride through the field on horseback. This places 
the rider’s vision above the tops of the Sudan grass and enables him to 
discover, from a considerable distance, plants which are off type. 
Johnson grass and Johnson-Sudan grass hybrids are much more diffi- 
cult to discover in a Sudan grass field. The only way to be sure there 
are nosuch plants in the field 1s to sow absolutely pure seed on land which 
is known to be free from Johnson grass. Roguing a field infested 
with Johnson grass, unless it be done with more than ordinary care, 
will not insure the removal of all the plants. It is well, then, for 
both buyer and producer to remember that preventing contamination 
is the only safe plan for dealing with Johnson grass, because it is so 
much like Sudan grass in appearance. 
All rogues should be removed before the Sudan grass has come 
into bloom, in order to preclude any chance of cross-pollination. _ 
THRASHING AND CLEANING THE SEED. 
Sudan grass can be thrashed in an ordinary grain separator if care 
is used in regulating the air blast so that seed will not be blown over 
into the straw pile. The sieves which are used in thrashing wheat or 
sorghum can be used for Sudan grass. If dry, the straw will run 
through the machine without clogging, but when not well cured or 
somewhat moist at thrashing time it may be desirable to top the 
bundles, so that only the heads need to be run through. 
Prices paid in 1920 for thrashing in Oklahoma and Texas varied 
from 50 cents to $1 per hundredweight, depending on whether the 
crew is furnished with the machine and on the quantity of grass to be 
thrashed. The thrashed Sudan grass makes a good roughage for 
either horses or cattle. Many stockmen believe it equal to prairie 
hay in feeding value. 
A farmer may flail out small quantities of Sudan grass for his own 
seeding. If this is done, the grass should be thoroughly dry before 
it is placed on the canvas. Seed thrashed in this way has to be 
