CROP ROTATION IN RELATION TO SOIL PRODUCTIVITY 
37 
These experiments on wheat, corn, and oats at Wooster show that 
rotation of crcps. when joined to the use of chemical fertilizer, is 
56.1 per cent as effective in increasing crop yields as the use of 
chemical fertilizer when joined to rotation of crops, as is indicated 
by the relative values of R. When compared with the use of manure, 
rotation (R) has a higher efficiency than when compared with the use 
of chemical fertilizer, as is indicated by an average relative value of 
81.0 per cent for R. 
The figures in the last two subcolumns show that the conjoint 
effects of rotation and the use of fertilizers, in effecting increases 
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Fig. 4.— Chart summarizing the rotation and fertilizer results obtained on wheat, corn, and oats 
at Wooster, Ohio, showing the average yields that have been obtained from cultivation alone, 
the increases effected when to cultivation is added rotation or the use of fertilizer, and the in- 
creases obtained (over cultivation; due to the conjoint effects of rotation and the use of fertilizers. 
The numbers below the bars are the plot numbers 
above the check-plot yields in continuous culture, are practically 
fully additive, except in case of the combined effects of rotation and 
the use of chemical fertilizer on wheat, where the effects are more 
than fully additive. 
In Figure 4 are summarized in diagrammatic form the results 
obtained at Wooster, as follows: The average yields of wheat, corn, 
and oats that have been obtained from cultivation alone, that is. with- 
out rotation and fertilizer: the increases obtained when with culti- 
vation is combined the practice of crop rotation or the use of ferti- 
lizer: and the increase over cultivation due to the combined effects 
of rotation and the use of fertilizer. 
