2 BULLETIN 546, U. S. DEPARTMENT OF AGRICULTURE. 



gators hare made field studies ( f 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 

 Scottsbluff Experiment Farm, a field station of the Bureau of Plant 

 Industry. 



The favorable results secured at Scottsbluff 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 Proj ect 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 

 the 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 ■ 

 years, 

 1908 to 

 1916. 



Period of experiment. 



Period covered. 



1913 



1914 



1915 



1916 





14.05 

 3.75 



2.15 



12.53 

 4.50 



11.70 

 3.24 



21.02 

 2.95 



13.95 













1.84 



2.52 



1.99 

















i Knorr, Fritz. Experiments with crops under fall irrigation at the Scottsbluff Reclamation Project 

 Experiment Farm. U. S. Dept. Agr. Bui. 133, 17 p., 5 fig. 1914. 



2 The writers desire to acknowledge their indebtedness to Mr. O. It. Mathews, Assistant, Dry-Land 

 Agriculture Investigations, for assistance in the conduct of these experiments. 



