Experimental Ph)ts at Rothamsted, from 1864 1883. 429 
crop has been placed upon the land every year, while for its 
nitrogen the crop has been left dependent upon the supplies fur- 
nished by the soil and atmosphere. 
In the following table will be seen the produce of this plot 
for 4 periods of 8 years each : and, for comparison, there is also 
given the produce of the permanently unmanured crop over a 
similar period. 
Table XXII. — Showing the Produce of Dressed Grain, and Total 
Produce (Corn and Straw) upon Plot 3 (the Permanently Un- 
manured Plot), and Plot 5, which has received Mixed Minerals 
for a period of 32 Years, divided into 4 periods of 8 Years. 
Without 
Manure, 
3. 
Mixed 
MiDe»ls, 
5 
Without 
Manure, 
3- 
Mixed 
Minerals, 
6. 
Dressed 
Com. 
Dressed 
Com. 
Total Produce 
Com and Straw. 
Total Produce 
Cora and Straw. 
8 years, 1852-1859 .. .. 
8 years, 1860-1867 .. .. 
8 years, 1868-1875 .. .. 
8 years, 1876-1883 .. .. 
bushels. 
13J 
12i 
m 
bushels. 
19 
15J 
14 
12i 
lbs. 
2736 
2183 
1833 
1610 
lbs. 
3191 
2450 
2144 
189& 
32 years, 1852-1S83 .. .. 
40 years, 1844-1883 .. .. 
13J 
14 
15i 
2090 
2244 
242i 
During the first 8 years of the experiment plot 5 received 
salts of ammonia, as well as mineral manures, and the average 
produce of wheat during these first 8 seasons was 29 bushels 
per acre, or 12 bushels annually in excess of the produce in the 
unmanured plot ; while during the first 8 years of the mixed 
minerals, without the salts of ammonia, the average produce 
has been 19 bushels per acre, or nearly 3 bushels more than the 
permanently unmanured produce. 
In the second period of 8 years the produce of the mixed 
minerals' plot has amounted to 15;^ bushels per acre, as against 
13^ bushels grown by the unmanured plot, a difference of 
If bushels in favour of the mixed minerals' plot. In the third 
period of 8 years, the produce of plot 5 was 14 bushels per 
acre : and in the last period of 8 years, it was 12^, or rather 
more than 12^ bushels per acre. 
The whole period of 32 years has thus given an average of 
15;j bushels on the mixed minerals' plot, as against 13|^ bushels 
upon the permanently unmanured plot ; and if we take the 
average produce of the unmanured plot for 40 years, the yield 
has been 14 bushels per acre. The application, therefore, of a 
