EFFECT OF FALL IRRIGATION ON" CROP YIELDS. 



The experiments were conducted in duplicate each year, the seven 

 plats in Series I duplicating those in Series III, while the plats in 

 Series II and IV were duplicates. The following crop varieties were 

 used: Oats, Great Dane in 1914 and Swedish Select in 1915 and 1916; 

 sugar beets, South Dakota No. 40 in 1914 and Kleinwanzleben in 

 1915 and 1916; flax, Minnesota No. 25; potatoes, Eureka in 1914 

 and 1915 and U. S. No. 4452 in 1916; barley, Minnesota No. 6 in 

 1914, Himalaya (Guy Mayle) in 1915, and Chevalier in 1916; corn, 

 Payne White Dent in 1914 and 1916 and Martens White Dent in 

 1915; and wheat, Defiance in 1914, Pringle Champlain in 1915, and 

 Marquis in 1916. The positions occupied by the crops on each of 

 the four series each year, the crop sequence on each plat during the 

 3-year period, and the number of summer irrigations applied are 

 shown in Table II. 



Table II . — Sequence of crops and number of irrigations applied to each in the fall-irrigation 

 experiments at the Belle Fourche Experiment Farm in 1914, 1915, and 1916. 





1914 



1915 



1916 



Plat. 



Crop. 



Num- 

 ber of 

 irriga- 

 tions. 



Crop. 



Num- 

 ber of 

 irriga- 

 tions. 



Crop. 



Num- 

 ber of 

 irriga- 

 tions. 



No. 7 





3 

 3 

 2 

 4 

 2 

 3 

 2 





1 



2 

 1 



1 

 1 

 2 

 2 





1 



No. 8 





Flax 





1 



No. 9 



Flax 







2 



No. 10 







Wheat 



1 



No. 11... 









1 



No. 12 





Wheat 





1 



No. 13 



Wheat 





Flax 



1 













As shown in Table II, an intertilled crop followed a close-plantedl 

 crop on each plat except No. 13 in 1915 and 1916 and No. 10 in 1916. j 

 More irrigation was necessary in 1914 than in either 1915 or 1916, as; 

 the growing season of 1914 received somewhat less rainfall than either! 

 of the others. The variations in both crop sequence and summer, 

 irrigation were the" same on all four series. 



All cultural operations on the four series were uniform as to both 

 character and time of performance throughout the period of experi- 

 ment. These included the ordinary operations incident to the pro- 

 duction of the seven field crops involved. The land was manured 

 from October 6 to 10, 1915, when 12 tons per acre of well-rotted 

 barnyard manure were applied uniformly to all the plats. 



RESULTS OF THE EXPERIMENTS. 



In the conduct of these experiments attention was directed chiefly 

 to the crop yields secured on fall-irrigated land as compared with 

 those of land not so irrigated and to the soil-moisture conditions on 

 the two groups of plats, particularly before the first summer irri-j 

 gation each season. It was to be expected that any important 



