40 
BULLETIN 1377, U. S. DEPARTMENT OF AGRICULTURE 
grown in rotation, and on the third, corn, oats, and clover (in rotation). 
The north half of each plot is untreated, whereas the south half 
receives standard applications of manure with cover crops (in the 
one-crop and two-crop systems). Rock phosphate is applied to the 
southwest one-fourth of each plot at the rate of GOO pounds, and 
steamed bone meal to the southeast one-fourth at the rate of 200 
pounds per acre per year. In 1904 ground limestone was applied at 
the rate of 1,700 pounds per acre to the south half of each plot/' 
(6, pp. 486 and 487.) 
These experiments were begun in 1SSS on land formerly highly 
productive. Comparable yields of corn — that is, yields on fertilized 
and unfertilized land in continuous culture and in rotation, begin 
with the year 1904 — corn being the only crop that is grown in con- 
tinuous culture. 
The Morrow plots are located on a prairie soil described as a brown 
silt loam which has probably developed from the weathering of 
glacial material deposited during the early Wisconsin glaciation. In 
reaction the soil had become somewhat acid. 
In Tabic 39 arc given the comparable yields of corn obtained in 
continuous culture 4 ami in rotation at Urbana. 
Table 39. — Yields of corn in continuous culture and in rotation, Urbana, III., 
1904 1916 
Vears 
Continuous culture ' 
Rotation (corn, cuts, 
and clover) 
Fertilized 
(MLP)i 
Unfer- 
tilized 
Fertilized 
(MLP)' 
i rnier- 
tilized 
Bushels 
55.3 
1904.. 
Bushels 
17.1 
48.7 
54.6 
32.0 
10.8 
Bushels 
21.5 
29.0 
35.9 
19.4 
11.2 
Bushels 
72.7 
1907 .. 
93. 6 80. 5 
1910... 
83.3 58.6 
1913 
47.8 33.8 
1916 
40.6 ' 27.8 
32.6 
23.4 
67.6 
51.2- 
1 A cover crop is grown on the continuous-culture plot, but not on the rotation plot. This balances, at 
least in part, the heavier applications of manure made on the rotation plots. 
» M(manure), standard application, the quantity that can be produced from the produce grown. P(phos- 
phorus), bone meal and rock phosphate. L (pulverized limestone). 
The results of a study of the average yields given in Table 39 are 
summarized in Tables 40 and 41. 
Table 40. 
of rotation and of the use of fertilizers on the yields of Corn, 
Urbana, III. 
[Rotation and fertilization practiced separately] 
Relative 
value of 
Increase 
rotation, as 
Average 
over check 
compared 
Cultural conditions 
yield per 
plot in 
with 
acre 
continuous 
fertilizers, 
culture 
in effecting 
larger 
yields 
Bushels 
Bushels 
Per cent 
Crop rotation without the use of fertilizers (r) 
51.2 
27.8 
302.2 
Use of fertilizers without rotation (0 
32.6 
9.2 
23.4 
