66 



CHAPTER V 



Before discussing the reasons for rotative cropping and 

 the conditions modifying this form of cropping, the following 

 results of experiments might be given : — 



Summary of Results of Crop Rotation in Adgell Field, Rothampstead, 

 Since 1848. 



The rotation practised was the Norfolk four-year rotation, 

 i.e., turnips, barley, clover and wheat. In this rotation the 

 clover is cut as hay, but a fair aftermath is ploughed in. The 

 above experiment is probably the most authoritative of its kind, 

 and shows clearly that a rotation, without the application of 

 fertilisers, will not maintain yield. 



Effect of different cropping systems on yield of Maize — 

 Illinois University. 



Crop years. 



Crop System. 



Average 



yield during 13 



year experiments, 



Average 

 yield during 29 

 year experiments 



1905-6-7 etc. 

 1903-5-7 etc. 

 1901-4-7 etc 



Maize continuously. 

 Maize and Oats. 

 Maize, Oats and Clover 



35 Bushels. 

 62 Bushels. 

 66 Bushels. 



27 Bushels, 

 46 Bushels. 

 58 Bushels. 



Several points should be noted in this experiment : (1) the 

 increase in yield over maize grown continuously by simply 

 changing the crop every year ; (2) that a good cropping system 

 in itself gives a tremendous advantage over crops grown con- 

 tinuously, still without the addition of fertilisers the yield is not 

 increased or even maintained. The land on which this experi- 

 ment was conducted originally yielded 70 bushels of maize per 

 acre. " Undoubtedly the rapid reduction during the first 12 



