102 
It is approximately correct, as stated by the Bureau of Soils, a that "the yield of 
wheal in this same experiment, where mixed mineral and nitrogenous manures had 
been used in some part of the rotation, had not been sensibly larger [than where no 
manure was used]," but the fact appears to have been overlooked that the root crop 
immediately following wheat has produced, during the forty-eight years, an average 
annual yield of 1.2 tons without fertilizing, and an average yield of 15.4 tons where 
mixed mineral and nitrogenous manures were used. If it were the physical condi- 
tion which so markedly affected the yield of wheat, it certainly failed utterly in' 
benefiting the root crop. 
In addition to this we have the simple fact reported by Lawes and Gilbert h that 
during the forty years, from 1852 to 1891, where mixed mineral and nitrogenous fer- 
tilizers were used the yield of wheat averaged 884 bushels when grown in this rota- 
tion, and 36J bushels when grown continuously. We might presume from these 
data that the higher yield produced where wheat was grown continuously is due to 
the improved physical condition of the soil, but more probably it is due to the fact 
that the crops grown continuously received somewhat heavier applications of plant 
food than the rotation crops. This shows, for comparison, the results obtained in the 
four-year rotation at Rothamsted when the roots were either fed off by sheep or cut 
and spread on the land. In this case only two crops were removed in four years, 
and yet the average yield of wheat was sensibly higher, and the yield of barley 
markedly higher, where mixed mineral and nitrogenous manures were used than 
where no plant food was applied. 
Yield of crops grown in four-year rotation at Rothamsted a (roots, barley, fallow, and 
wheat). Roots not removed (fed or spread on land). 
Number of course. 
First 6 
Second 
Third 
Fourth 
Fifth 
Average 2 to 5.. 
Sixth 
Seventh 
Eighth 
Ninth 
Average G to 9.. 
Tenth 
Eleventh 
Twelfth 
Thirteenth 
Average 10 to 13 
Average 2 to 13. 
Roots 
tons. 
Barley, 
bushels. 
Wheat, 
mshels. 
Applied — 
Applied- 
Applied- 
Nitrogen, 
Nitrogen, 
Nitrogen, 
No plant 
phos- 
phorus, 
No plant 
phos- 
phorus, 
No plant 
phos- 
ph< rus, 
potas- 
potas- 
potas- 
sium. 
sium. 
sium-. 
8.9 
21.4 
45 
44 
31 
27 
1.4 
19.5 
33 
37 
37 
37 
1.7 
17.0 
44 
67 
35 
40 
.1 
4.4 
33 
58 
42 
49 
.4 
9.3 
35 
47 
23 
20 
1.0 
12.6 
36 
52 
34 
37 
.0 
.0 
21 
38 
14 
17 
2.5 
16. G 
21 
47 
24 
30 
1.6 
18.9 
22 
45 
12 
10 
1.9 
22. 8 
31 
48 
34 39 
1.5 
14.6 
24 
45 
•21 24 
1.0 
14.8 
23 
32 
33 
41 
1.2 
21.2 
17 
23 
31 
45 
.6 
25.0 
19 
2G 
2H 
32 
1.2 
16. 6 
13 
35 
27 
39 
1.0 
19.4 
18 
29 
29 
39 
, 2 
15.5 
26 
42 
28 
33 
a Memoranda of the origin, plan, and results of the field and other experiments at Rothamsted (1900), 
pp. 114, 115. 
''Clover instead of fallow in first course. 
In connection with the very extensive and truly valuable data furnished by the 
Bureau of Soils in this bulletin and the conclusion ' drawn, that "all types of soil 
furnish about the same amount of plant food when treated with the same propor- 
tion of water, other conditions as time, temperature, etc., being also the same," it 
«U. S. Dept. Agr., Bureau of Soils Bui. 22, p. 56. 
''Agricultural Investigations at Rothamsted, V. S. Dept. Agr., Office of Experi- 
ment Stations Bui. 22, pp. 151 and L89. 
^U. S. Dept. Agr., Bureau of Soils Bui. 22, p. 46. 
