Experimental Plots at Rothamsted, from 1864 to 1883. 427 
per acre, or nearly 4 bushels below the produce of the previous 
10 years. In the fourth period of 10 years, the average produce 
was only 10;^ bushels per acre. 
It is well known to all those connected with the land in 
Great Britain that the seasons have latterly been most unfa- 
vourable for the growth of wheat. It is therefore evident that 
the produce of the last 10 years does not correctly represent the 
reduction due to exhaustion of the soil alone. This, indeed, is 
proved bv the fact that, under the influence of a rather better 
season, the produce of the last crop in 1883 was 13f bushels 
per acre, which very nearly represents the average yield of the 
40 crops. 
In our paper on " Home Produce, Imports, and Consump- 
tion," we made some attempts to calculate what was the annual 
decline in the produce due to exhaustion — irrespective of vari- 
ations due to good or bad seasons — and it would appear probable 
that, up to a certain period, the decline might amount to about 
•J of a bushel per acre per annum — equal to a gross produce 
in corn and straw of 40 lbs. per acre. 
It is evident, however, that with each decline the reduction 
will become less and less. Atmospheric influences, and even 
the small amount of ammonia brought down in the rain, will 
form a larger factor upon a declining crop. It is evident, 
therefore, that the actual process of the exhaustion of the soil 
differs considerably from all the preconceived ideas upon the 
subject. The soil, in fact, not only contains more fertility, but 
also holds it with a much firmer grasp, and parts with it less 
readily than we had previously imagined. 
The average amount of produce in straw and corn removed 
has been 1 ton per acre, containing about 2000 lbs. of abso- 
lutely dry matter ; and we have very strong evidence, derived 
from other experiments in the field, to prove that carbon and 
organic matter, generally, are derived from the atmosphere, 
while nitrogen and mineral matters are taken from the soil. 
This would divide the products into from 94 to 95 per cent, 
atmospheric, and from 5 to 6 per cent, soil compounds. 
The average amount of soil compounds annually removed by 
this unmanured wheat crop is from 100 lbs. to 120 lbs. per acre ; 
and of the three most important constituents of plant growth there 
have been removed 17 lbs. of potash, 10 lbs. of phosphoric acid, 
and 20 lbs. of nitrogen. Such are the results obtained up to the 
present time, and they may be summed up as follows : — Upon 
a field which has been under arable cultivation certainly for two 
or three centuries — and possibly for a much longer period — and 
which has consequently lost a very considerable amount of its 
original fertility, we find — after the removal of 40 unmanured 
