SUDAN GRASS AND RELATED PLANTS. 59 



for any length of time. In humid regions it is profitable to protect 

 the grass with shock covers; otherwise the seed will be damaged by 

 wet weather. 



The proper time for harvesting must be decided very largely by the 

 grower. Sudan grass tillers freely, and this gives rise to a progressive 

 ripening of seed panicles; those on the main stem ripen first and those 

 on the tillers mature successively in the order of their age. The period 

 of ripening is thus continued almost indefinitely. Sudan grass seed 

 does not shatter easily. Harvesting, therefore, may de delayed for 

 several days after the panicles on the main stems are mature without 

 any particular loss unless high winds prevail, birds are abundant, or 

 the stems become so weakened by red-spot that they break down. 

 Because of these risks it is well not to wait too long after the first 

 heads are ripe, and in addition the gain in seed from the ripening 

 tillers will not be sufficient to balance the loss of hay or pasture from 

 the aftermath. Obviously, the earlier the seed crop is taken off the 

 larger will be the aftermath. 



It is best, then, to watch the crop carefully and harvest as soon as 

 the main stems have fully ripened their seed unless the seed crop from 

 the main stems promises to be small as compared with that from the 

 tillers. Immature heads usually ripen considerably in the shock. 



The crop is ready for thrashing after it has been in the shock for 

 two or three weeks, if good curing weather has prevailed. There is 

 danger in stacking the seed crop unless it is thoroughly cured. Sudan 

 grass has a large amount of sap in the stems and will often heat in the 

 stack and injure the germination of the seed even if stacked when the 

 leaves are fully cured. It is usually safer to use shock covers to pro- 

 tect the seed from rain and birds and leave the crop in the field until 

 it is thrashed. 



CARE NECESSARY TO PREVENT HYBRIDIZATION. 



Sudan grass crosses very freely with all sorghums, but especially 

 with the sweet sorghums, such as Minnesota Amber. Extreme care 

 is necessary, therefore, to prevent the hybridization of Sudan grass 

 and sorghum in field plantings where a seed crop is to be harvested. 

 There is usually little danger of cross-pollination if the Sudan grass 

 field is 100 yards from any sorghum, but on the Great Plains, where 

 the atmosphere is usually in motion, pollen may be carried for a 

 greater distance. Under such conditions 60 to 80 rods is not too 

 far to have fields of these two crops separated. 



Another source of cross-pollination is the volunteer sorghum 

 growth sometimes found in Sudan grass fields. This trouble can be 

 avoided by seeding the grass on a field which has been planted to 

 some crop other than sorghum the preceding year, or by careful 

 roguing before the Sudan grass or sorghum has headed. The sor- 



