20 BULLETIN 981, U. S. DEPARTMENT OF AGRICULTURE. 
crops reported to have grown without rain are usually found to have 
used soil moisture previously stored or to have been favored by the 
natural run-off from adjoining areas. 
Sudan grass has sometimes given good returns under dry farming 
in the Southwest at places where the normal annual rainfall is but 8 
to 15 inches. It yields much more, however, in the southern Great 
Plains area, where the annual rainfall is between 20 and 30 inches. 
Growth is abundant in the Southeast, where the rainfall is 40 to 60 
inches, but this humidity permits the sorghum midge to thrive, which, 
as explained elsewhere, prevents seed production. Where the rain- 
fall is about 60 inches and the altitude mostly below 100 feet, as in 
Florida and other Gulf and Atlantic coast points, Sudan grass pro- 
duction is usually not profitable, owing to the disease known as red- 
spot, orsorghum blight. Heavy rainfall, in addition to cold, accounts 
for the failure of Sudan grass reported within 10 or 20 miles of the 
Pacific coast in northern California and Oregon. The crop has shown 
ability, however, to survive inundation for several days as well as 
corn or any of the sorghums if the soil is drained well. 
TasBLe I.—The water requirements of Sudan grass and other staple crops, as determined 
by experiments at Garden City, Kans., and Akron, Colo. 
[The data under “ Ratio’’ show the number of pounds of water required to produce 1 pound of dry matter.] 
| At Garden City, Kans., 1915 (16, pp. 483-484). At Akron, ek 1912 (4, pp. 
Crop plant. | 
] | 
Varieties. | Period of growth. Ratio. Varieties. Ratio. 
apes oe Be eee. | (Eee OS ee Pea Sees Seen) EH 
Gornetes Pride of Saline. .._.- May 22 to Aug. 25.../ 2674 2 | Average of 8........ 286 
RCT eee ee Dwarf Blackhull....| May 22 to Sept. 11...) 2214+ 2 | Blackhull........... 25945 
Milos cea DD Wariiss cece eee May 22 toSept. 32451 24442) 3 Diwarte-- ose see eee te 27344 
So epee Amber... 239+2 
SUES USSR a Sogcns- gente gee kb tore Piobreta ag stp oe OSS ODO OE es Red Amber........- 23744 
Germanee eee 248+7 
Millet......------ FoR 86s 2 8s aac e Poo cess see aces sons ae an ace Kupskes go a 18742 
Hefeniaes 2-2 oe- ie fce case sews cecsacesce|, May.22:40.56pbe Gane] y 240] soe ee eee ee ee mere ee ee 
Sudan grass....- Beea ee esgs senso Stee Mays22 to Sepied4> 1300451 oleae ee eee 35942 
The water requirements of Sudan grass and several other crops 
were determined on the basis of the total dry matter, exclusive of that 
in the roots, by Briggs and Shantz in 1912 at Akron, Colo., and by 
Miller in 1915 at Garden City, Kans., as shown in Table I. These 
results indicate in a general way that Sudan grass uses more water 
in the production of a pound of dry matter when the supply of soil 
moisture is abundant than the other sorghums, the millets, or corn. 
In the tests at Garden City, Kans., and Akron, Colo., the plants 
were grown under optimum soil-moisture conditions; that is, the soil 
was supplied regularly with all the water the plant could use. This 
condition, of course, did not simulate in the least degree the soil 
conditions ordinarily found in a semiarid region, where drought 
endurance is an important factor in crop production. It is impossible 
