CROP ROTATION IX RELATION TO SOIL PRODUCTIVITY 
25 
Table 21. — Effects of crop rotation and of the use of fertilizers on the yields of wheat, 
corn, and oats at Columbia, Mo. 
[Rotation and fertilization practiced separately] 
Crop 
Cultural conditions 
Average 
yield 
per acre 
Relative 
value of 
i crop rota- 
tion, as 
compared 
o™"h™ ' with fer- 
continu- tilizers> 
Average 
increase 
over 
check 
plot in 
ous 
culture 
(c) 
in effect- 
ing larger 
yield 3 
Wheat. . . Crop rotation without use of manure (r) . 
I Use of manure without rotation (f) 
Crop rotation without use of chemical fertilizer (r). 
! Use of chemical fertilizer without rotation (/) 
C orn C rop rotation without use of manure (r) _ _ 
; Use of manure without rotation (/) 
Oats ' C rop rotation without use of manure (r) 
1 Use of manure without rotation (f) 
Bushels Bushels 
Per cent 
19.1 
19.1 
20.1 
26.4 
37.5 
37.1 
27.6 
33.1 
10. 100. 
10.0 
7. 6 54. 7 
13.9 
15. 1 102. 7 
14.7 
6. 2 53. 
11.7 
These average results show that, under the conditions of the Mis- 
souri experiments, crop rotation without the use of manure is as 
effective in increasing the yields of wheat and corn, over the check 
plots in continuous culture, as a mean annual application of 6.8 
tons of manure without rotation. In case of oats, rotation proved 
to be slightly more than half as efficient as the use of manure. 
The 6-year rotation of corn, oats, wheat, clover, timothy, and 
timothy practiced without the use of any fertilizer, is 54.7 per cent 
as efficient in increasing the average yield of wheat over cultivation 
alone as an annual application of a chemical mixture consisting 
of 495 pounds of sodium nitrate, 209 pounds of acid phosphate and 
111 pounds of muriate of potash. (See Table 22.) 
ROTATION AXD THE USE OF FERTILIZERS CONJOINED 
Since, in the Missouri experiments, the same quantities of manure 
have been applied per acre annually on all the plots herein considered 
(mean application of 6.8 tons per acre), the results in Tables 17, 18, 
19, and 20, showing the separate effects of rotation and the use of 
fertilizers, are comparable with the results showing the combined 
effect of these two practices. As regards the use of chemical fer- 
tilizers on wheat, the quantity that has been applied per acre in con- 
tinuous culture for the 6-year period is 553 pounds less than the total 
quantity applied to the crops in the 6-year rotation. This is shown 
in Table 22. 
Table 22. — Application of chemical fertilizer in rotation and continuous culture, 
Missouri 
Plot number Crop 
Kind and quantity of ferti- 
lizer materials used (annual- 
ly per acre) 
Total quantities for 6-year 
period (per acre) 
Sodium Acid 
nitrate phosphate 
Muriate 
of potash 
Sodium 
nitrate 
Acid 
phosphate 
Muriate 
of potash 
2 (rotation) Corn... 
Pounds ! Pounds 
764 301 
Pounds 
136 
Pounds 
3,336 
2,970 
Pou nds 
1,206 
1,254 
Pounds 
; Oats 
375 157 98 
495 209 111 
774 245 216 
464 147 170 
Wheat 
j Clover 
901 
i Timothy... 
do... 
2 (continuous cul- ; Wheat 
464 147 
495 209 
170 | 
111 
666 
ture) 
60635—261 
