20 



BULLETIN 991, U. S. DEPARTMENT OF AGRICULTURE. 



reasonably be expected to overcome the effect of the seasonal condi- 

 tions as fully as any cultural method. There should at least be offered 

 as wide a contrast between fallow and cropped land in their control 

 by seasonal conditions as between any methods that might be selected. 

 In rotation No. 5 wheat is on fallow, and in rotation No. 8 it fol- 

 lows oats. In rotation No. 8 the oat crop is on fallow and in No. 5 it 

 follows wheat. The yields of these two crops in these rotations are 

 given in Table II for each year of the 14-year period from 1906 to 

 1919. In 1906, the first year, neither plat was on fallow, but all 

 were on land in variety tests of small grain in 1905. The yields 

 from 1907 to 1919 are shown graphically in figure 4. The upper 

 portion of this diagram gives the yields of oats and the lower por- 

 tion the yields of wheat. The yields on fallow are shown by circles 

 connected by a solid line and the yields on land producing a crop 

 the year before by crosses connected with a broken line. Both the 

 figures of yield and the diagram are so clear as to need little com- 

 ment. The yields of both methods go up or down with the seasons 

 to a degree altogether disproportionate to any differences between 

 the methods themselves. 



Table II. — Annual yields of lolieat on fallow in rotation No. 5 and following 

 oats in rotation No. 8, and of oats on fallow in rotation No. 8 and following 

 vjheat in rotation No. -5, showing the controlling effect of seasonal conditions 

 at Edgeley, N. Dak., during the 14-year period from 1906 to 1919, inclusive. 





Yields per acre. 



Year. 



Yields per acre. 



Year. 



Wheat. 



Oats. 



Wheat. 



Oats. 



Rota- 

 tion 

 No. 5. 



Rota- 

 tion 

 No. 8. 



Rota- 

 tion 

 No. 8. 



Rota- 

 tion 

 No. 5. 



Rota- 

 tion 

 No. 5. 



Rota- 

 tion 

 No. 8. 



Rota- 

 tion 

 No. 8. 



Rota- 

 tion 

 No. 5. 



1906 



Bushels. 

 15.8 

 30.3 

 11.8 

 19.5 

 29.8 

 7.8 

 2.7 

 39.0 

 25.3 



Bushels. 

 15.0 

 27.5 



8.5 

 10.3 

 26.6 



6.3 



.7 



28.2 



17.1 



Bushels. 

 50.0 

 63.8 

 30.9 

 20.9 

 56.2 

 10.0 

 6.1 

 72.5 

 46.2 



Bushels. 

 55.6 

 57.5 

 27.5 

 33.4 

 63.7 

 13.7 

 4.4 

 65.9 

 36.2 



1915. 

 1916. 

 1917. 

 1918. 

 1919. 





Bushels. 

 38.7 

 9.2 

 10.0 

 20.5 

 1.7 



Bushels. 

 37.0 

 10.5 

 13.3 



7.0 

 2.8 



Bushels. 

 100.7 

 26.9 

 8.1 

 27.8 

 11.6 



Bushels. 

 82.2 



1907 . 





19.1 



1908 . 





16.9 



1909... 





15.6 



1910... 





22.8 





Average, 

 1907-1919. 





1912 



17.8 



14.1 



36.0 





1913 



35.2 



1914 











Several causes conspire to make this so, or there are several 

 reasons why it is so. The season may be so dry, as in 1910 and 

 1911, that both methods are more or less complete failures, or the 

 season may be so wet that both methods produce heavily, as in 1912 

 and 1915. The fallow season may be so dry that it is impossible to 

 store water in the fallow, in which case it possesses no advantage 

 in this resjoect over a cropped plat, or the rainfall between harvest 

 and seeding may be so abundant that the cropped as well as the 

 fallow plat is filled with water, in which case again the fallow would 

 have no advantage so far as water supply is concerned. This is an 

 especially common occurrence in a shallow soil of limited water- 

 storage capacity and with a rainfall as high as that at Edgeley. 

 Another factor that equalizes yields by reducing all to a common 



