10 BULLETIN 836, U. S. DEPARTMENT OF AGRICULTURE. 



from the free water surface of a tank 8 feet in diameter. The 

 evaporation was more than three times as great as the precipitation 

 during that period. The maximum monthly evaporation, 11.7 

 inches, in this 5-year period, occurred in July, 1917. During that 

 same month the precipitation amounted to only 1.1 inches. The 

 5-year average evaporation for July was 10.6 inches, and that of the 

 precipitation 1.4 inches. The averages for August are 8 inches of 

 evaporation and 3.1 inches of precipitation. Such high evaporation 

 and low precipitation have a bad effect on plant growth and are 

 contributing causes to certain unfavorable crop results in various 

 years. 



THE WOODWARD FIELD STATION, 



The Woodward Field Station, located 1 mile southwest of the 

 main part of Woodward, Okla., was established by the Office of 

 Dry-Land Agriculture during the autumn of 1913, and the first crop 

 was produced the following season. The farm consists of 160 acres 

 of bench land. Most of the soil at the station is a light phase of 

 sandy loam which is classified as Canadian sandy loam. Some soil 

 blowing has occurred at the station but has never been serious. 



Woodward is centrally located in the western broom-corn area, and 

 conditions are fairly representative of the transition belt which 

 extends north and south between the high plains on the west and the 

 prairie region to the east. The principal crops of the surrounding 

 country are milo, kafir, broom corn, and winter wheat, with some 

 corn and alfalfa grown on bottom lands. The results of the experi- 

 ments with broom corn at this station should be applicable to the 

 greater part of the western broom-corn area. 



THE BROOM CORNS. 



Broom corn is a specialized sorghum, closely related to sweet sor- 

 ghum. It consists of two rather distinct groups of varieties. These 

 react differently to environmental conditions and therefore give dif- 

 ferent results. To understand these results it is necessary to know 

 the characters by which the groups differ from each other. 



CLASSIFICATION. 



The two groups of broom corn differ mainly in the height of the 

 plants, in the tenacity of the attachment of the peduncle to the up- 

 per node, and in the length and texture of the brush. 



Standard broom corn grows to a height of 8 to 10 feet under the 

 conditions obtaining at the Woodward Field Station. Under more 

 favorable conditions farther east it reaches a height of 12 to 15 feet. 

 The leaves vary from 9 to 11 in number. The heads range in length 

 from 18 to 24 or more inches. They are well exserted from the boot 



