2 BULLETIN 546, U. S. DEPARTMENT OF AGRICULTURE. 
gators have made field studies of the subject. Knorr, 1 experimenting 
for three years on the North Platte Reclamation Project in western 
Nebraska with wheat, oats, barley, potatoes, sugar beets, and corn, 
found that the fall irrigation of the land on which these crops were 
to be grown increased the yield an average of 16 per cent. The 
yield increases secured in these experiments were ascribed to the 
fact that fall irrigation resulted in more moisture in the surface soil 
at seeding time in the spring and also in a better absorption of 
moisture by the soil to a depth of 6 feet during summer irrigation. 
These experiments were conducted on a sandy loam soil at the 
ScottsblufT Experiment Farm, a field station of the Bureau of Plant 
-Industry. 
The favorable results secured at ScottsblufT suggested the advis- 
ability of repeating the experiments at another point in the Great 
Plains area where the soil conditions are different from those at 
Scottsbluff. Accordingly, in the autumn of 1913 a series of fall- 
irrigation experiments involving oats, sugar beets, flax, potatoes, 
barley, corn, and wheat was inaugurated at the Belle Fourche Experi- 
ment Farm on the Belle Fourche Reclamation Project in western South 
.Dakota, The experiments with these seven spring-planted crops were 
-continued through 1914, 1915, and 1916. The results secured are 
reported in this bulletin. 2 
RAINFALL. 
During the nine years, 1908 to 1916, inclusive, the annual rainfall 
:at the Belle Fourche Experiment Farm ranged from 6.64 inches, in 
1911, to 21.02 inches, in 1915, the mean for the 9-year period being 
14; 05 inches. In connection with the problem of fall irrigation it is 
important to consider the distribution of the rainfall with reference to 
%ie fall period — the period between the beginning of harvest and the 
time of fall irrigation — and to the winter period. The mean rain- 
fall of these periods during the nine years of record and the actual 
rainfall during the time in which the fall-irrigation experiments were 
conducted are shown in Table I. 
Table I. — Precipitation at the Belle Fourche Experiment Farm, 1908 to 1916, 
inclusive. 
Mean, 
nine 
vears, 
1908 to 
1916. 
Period of experiment. 
Period covered. 
1 
1913 1914 
1915 
1916 
14. 0.5 
3.75 
2.15 
12.53 11.70 
4.50 j 3.24 
1 
21.02 
2.95 
13. 95 
Pall period (August to October, inclusive) 
1.84 
2. 52 
1.99 
1 Knorr, Fritz. Experiments with crops under fall irrigation at the Scottsbluff Reclamation Project 
Experiment Farm. TJ. S. Dept. Agr. Bui. 133, 17 p., 5 fig. 1914. 
2 The writers desire to acknowledge their indebtedness to Mr. O. R. Mathews, Assistant, Dry-Land 
Agriculture Investigations, for assistance in the conduct of these experiments. 
