126 



COBN CROPS 



yield. When additional minerals have been added, the 

 crop production has been actually increased about 20 

 per cent. 



At the Indiana station ^ five cropping systems have been 

 compared for 20 years, A\dth and without commercial 

 fertilizers. Without giving details, the following table 

 shows clearly enough the comparative effect of different 

 cropping systems on the maintenance of production. 



TABLE XXIII 



Indiana Experiments, comparing Corn Yields at Begin- 

 ning AND End of Twenty-year Period in Different 

 Rotations 



Ind. Agr. Exp. St.a., Circ. 25. 1911. 



