CROP ROTATION IN RELATION TO SOIL PRODUCTIVITY 
59 
INCREASING SOIL PRODUCTIVITY 
In Table 53 is given a summary of data calculated from previous 
tables, showing the relative value for crop rotation (r) and the 
conjoint effects of rotation and the use of fertilizers in increasing 
soil productivity. 
Table 53. — Relative value of rotation (r) and the conjoint effects of rotation and the 
use of fertilizers in increasing soil productivity 
Increase ! in 
Additive effects 
productivity 
of rotation and 
(over mainte- 
use of fertilizers 
nance yield) 
effected by- 
Rela- 
1 
Station Kind of fertilizer 
Main- 
tenance 
yield 
tive 
value 
for rota- 
tion (r) 
as com- 
pared 
with 
ferti- 
Aver- 
age 
yield, 
rota- 
tion 
con- 
joined 
Sum of 
Crop 
^fn^f -^tual 
itv ef- in pr0 " 
feLl ^uy- 
b >-- r °- ected 
tation . 
Rota- 
tion 
Use of 
ferti- 
lizer 
lizers in 
increas- 
ing soil 
produc- 
tivity 
with 
use of 
ferti- 
lizer 
and use 
of fer- 
tilizer 
when 
prac- 
ticed 
sepa- 
rately 
(r-hfl 
Dy con- 
joint 
action 
of rota- 
tion 
and use 
of fer- 
tilizer 
Bush- 
Per 
Bushels els Bushels 
cent 
Bushels 
Bushels 
Bushels 
Wheat... 
Rothamsted.. Chemical fertilizer. 
17.5 6.6 . 6.1 
108.2 
32.5 
12.7 
15.0 
Columbia, do 
14. 2 8. 6 13. 4 
64.2 
32.5 
22.0 
18.3 
Mo. 
do Stable manure 
14 2 5.9 I 5.9 
100.0 
30.6 
11.8 
16.4 
booster, Ohio. {Ch^al^tUizer. 
10. 5 1. 5 9. 2 
16.3 
30.0 
10.7 
19.5 
10. 1 2. 7. 
28.6 
21.7 
9.0 
11.6 
Corn 
Columbia, do 
Mo. 
33. 5 5. 5 0. 3 

48.9 
5.8 
15.4 
Wooster.Ohio.g^ '-«<-; 
29.0 -2.6 5.4 
27. 2 -0. 6 ' 1.0 

47.9 
43.8 
2.8 
0.4 
18.9 
16.6 
Illinois Phosphate and 
41.6 9.6 -9.0 
67.6 
0.6 
26.0 
manure. 
Oats 
Columbia, Manure 
23. 6 5. 3 i 10. 6 
50.0 
37.5 
15.9 
13.9 
Mo. 
Wooster, Ohio. {g^ fe ^; 
27. 8 4. 4 11. 
40.0 
53.2 
15.4 i 25.4 
28. 4 3. 9 1.2 
325.0 
41.3 
5.1 12.9 
Barley... 
Rothamsted...' Chemical fertilizer- 
27.4 -6.4 14.6 
35.0 
8. 2 7. 6 
• Increases above maintenance yield effected by rotation and the use of fertilizer when practiced inde- 
pendently of each other. 
It is to be observed that, in 8 of the 13 experiments listed, the 
use of chemical fertilizer or manure, when practiced in the absence of 
rotation, is more effective in increasing productivity than rotation 
alone; and in 5 cases the effectiveness of rotation is equal to or greater 
than that of the use of fertilizer. And further, in all cases, except 
the barley test, the conjoint effects of rotation and the use of fertilizer 
are additive in increasing soil fertility — in 10 of the experiments the 
effects being more than fully additive. 
