12 
BULLETIN 1377, U. S. DEPARTMENT OF AGRICULTURE 
In the last two columns are given the increases in yields of both 
wheat and barley over the respective check plots in continuous 
culture. These gains express the absolute values of crop rotation 
and the use of fertilizers in effecting differences in yields on these 
particular plots. 
Table 2. — Comparative effects of crop rotation and the use of fertilizers on the yields 
of wheat and barley at Rothamsted (15) 
[Crop rotation and the use of fertilizer acting apart from each other] 
Field and plot No. Crop 
Agdell, rotation field 
6-0. 
Broadbalk, continu- 
ous culture: 
Wheat.. 
...do. 
...do. 
11.. 
5... 
.do 
..do. 
..do. 
Agdell, rotation field 
6-0. 
Hoos, continuous cul- 
ture: 
1-0 
1-A 
Soil treatment (fertilizers given in 
pounds per acre annually) 
..do | 
Barley.. ; 
..do.... 
.do.... 
Check plot, no fertilizer— rotation only. 
Check plot, no fertilizer... 
400 pounds ammonium salts • (86 pounds 
N, or 2N). 
400 pounds ammonium salts, 392 pounds 
superphosphato (2\*. P). 
792 pounds minerals, 5 no nitrogen (P, K) . 
Minerals and 200 pounds ammonium 
salts (N, P, K). 
Minerals and 400 pounds ammonium 
salts (2N, P, K). 
Minerals and 600 pounds ammonium 
salts (3N, P, K). 
Minerals and 550 pounds nitrate of soda 
(2N, P, K>. 
14 tons farm manure 
Check plot, no fertilizer— rotation only.. 
1-AA 
2-0 
2-A 
...do 
...do 
...do 
do 
4-0. 
4- A. 
4-AA. 
7-2... 
Check plot, no fertilizer 
200 pounds ammonium salts (43 pounds 
N). 
275 pounds nitrate of soda (43 pounds N) . 
392 pounds superphosphate (P) 
200 pounds ammonium salts, 392 pounds 
superphosphate (N, P). 
275 pounds nitrate of soda, 392 pounds 
superphosphato (N, P). 
792 pounds minerals, no nitrogen (P, K). 
Minerals and 200 pounds ammonium 
salts (N, P, K). 
Minerals and 275 pounds nitrate of soda 
(N, P, K). 
14 tons farm manure 
Average 
yield per 
acre (18 
crops) ' 
Bushels 2 
24.05 
12.33 
19.35 
22.62 
15.00 
23.58 
32.20 
36.68 
32.01 
34.90 
21. 81 
14.06 
24.87 
28.32 
20.38 
37.98 
43.80 
21.38 
41.89 
43.51 
48.04 
Increase 
due to 
rotation 
Bushels 
» 11.72 
Increase 
due to 
fertiliz- 
ers 
Bushels 
7.02 
10.29 
2.67 
11.25 
19.87 
24.36 
19.68 
22.57 
10.81 
K26 
6.32 
23.92 
29.74 
7.32 
27.83 
29.45 
33.98 
J The 18 crops of wheat or barley in continuous culture correspond to the 18 wheat or barley years in 
rotation. 
> Winchester or American bushels. One imperial or English bushel equals 1.032 American bushels. 
3 Difference in yield between check plots in rotation and in continuous culture. 
* In each case ammonium salts include equal parts of sulphate and chloride. 
* In each case minerals include 392 pounds of superphosphate, 200 pounds of sulphate of potash, 100 
pounds sodium sulphate, and 100 pounds of magnesium sulphate. 
In case of the wheat, it is to be observed that rotation effected a 
larger increase in vields than the following annual applications of 
chemical fertilizers in continuous culture: 400 pounds of ammonium 
salts; 792 pounds of a mixture of ammonium salts and superphos- 
phate; 792 pounds of mineral salts containing both phosphate and 
potash; and a mixture of chemicals containing, in addition to sodium 
and magnesium sulphates, 200 pounds of ammonium salts, 392 pounds 
of superphosphate, and 200 pounds of sulphate of potash. The effec- 
tiveness of the fertilizer applications made on plots numbered 7, 8, 9 a 
and 2 a (Broadbalk field) is, in each case, greater than that of rotation. 
