Erperimental Plots at Eothamsted, from 1864 to 1883. 445 
nitrogen on plot 2 will amount to, and possibly exceed 
8000 lbs. per acre. This would exceed the amount, to the 
same depth, on plot 7 by more than 1600 lbs., and that con- 
tained on the permanently unmanured land (plot 3) by more 
than 2200 lbs. 
By far the largest difference in the nitrogen of the three plots 
is found in the first 9 inches from the surface. At that depth 
the dunged land contained double the amount of nitrogen which 
is found on plot 3, and one and a half times as much as is 
found on plot 7 ; and we estimate that plot 3, after the 
removal of forty unmanured crops of wheat in succession, still 
contains about 2000 lbs. of nitrogen in the first 9 inches from 
the surface ; this, in fact, represents the residue of the natural 
fertility, or, to use a word imported into the Agricultural 
Holdings Act, of the inherent capability of the soil. 
The relation between the carbon and nitrogen in these three 
soils, which differ so greatly in their total amount of nitrogen, 
indicates that they do not differ much in their character. On 
the unmanured land the amount of carbon to 1 of nitrogen is 
not quite 10 ; on plot 7 it is 1 to 10^ ; and on the land which re- 
ceives dung it is not quite 1 to 12. Now the unmanured plot has 
received neither carbon nor nitrogen in manure ; plot 7 has 
received a very large amount of nitrogen, but no carbon ; while 
plot 2 has received a very large amount of both carbon and 
nitrogen. The relation between the carbon and nitrogen in the 
farmyard-manure is in the proportion of about 25 of carbon ta 
1 of nitrogen ; this proportion is totally different to what we 
find it in the soil. 
The close relation between the carbon and nitrogen in 
plot 3 and plot 7 indicates that the larger amount of nitrogen 
found in the soil of plot 7 is not due to the direct storing up of 
ammonia by the soil, but to the nitrogen forming part of 
vegetable growth, and being thus stored up in the stubble and 
roots. 
If the nitrogen of the salts of ammonia had been stored up in 
any form except that of vegetable growth, the relation of carbon 
to nitrogen would have been lower on plot 7 than on plot 3, 
instead of which it is higher. There is also very clear evidence, 
derived from analyses of the soil of plot 3 and plot 7, that of 
the two the latter contains by far the larger amount of unex- 
hausted fertility. 
In the adjoining field, where barley is grown continuously, 
we have not only the evidence of the same accumulation having 
taken place as shown by analysis, but we have the evidence of 
the crops themselves. For twenty years in succession, 14 tons 
