Law of Diminishing Returns 
231 
conducted at Rothamsted relating to sewage irrigation, malt and 
barley, ensilage, and the composition of the wheat grain and of 
milling products. 
The value of the book to practical agriculturists may be best 
shown by indicating some of the important results obtained 
from the experiments. 
Wheat has been grown continuously on the Rothamsted 
experimental plots for the long period of sixty years, a fact 
which is not only absolutely unique in itself, but which enables 
lessons to be learned that could have been taught in no other 
way. No one, for instance, could have ventured with any 
confidence to state what degree of fertility could be maintained 
in a soil devoted exclusively to the cultivation of wheat. The 
Rothamsted experiments prove the possibility of growing wheat 
annually for sixty years upon the same land with no manure 
whatsoever. And the treatment has resulted in an annual 
average yield of 13 bushels per acre, this being “almost the 
average crop produced in the United States, and very similar 
to the general average production of the great wheat-growing 
areas of the world.” On the other plots striking and definite 
results have been obtained with the continued use of farmyard 
manure and artificial fertilisers, all of which will well repay 
careful study. 
The book teems with significant facts and deductions, 
copiously illustrated by tables and graphic diagrams which 
greatly assist comprehension. Thus the law of diminishing 
returns by which “ each increment in the cost of production, 
whether labour or manure, gives rise to a smaller proportionate 
return, until a point, is reached when the value of the increased 
yield is more than balanced by the outlay required to bring 
it about,” is illustrated very clearly ; and the experiments 
indicate the amount of manure that will give profitable returns 
with wheat at certain prices. The practical deduction is that 
“ high farming (intensive cultivation and liberal expenditure 
on manure) is only justified in times of high prices and is 
no remedy for low ones.” A fact brought out and now 
generally acted upon is the evanescent character of nitrogenous 
applications like nitrate of soda and sulphate of ammonia. 
The effect of these are shown to be limited to the season of 
their application, whereas mineral manuring is carried forward 
and has effect in future seasons. 
Another interesting point illustrated is the effect of the 
weather during seed time and winter upon the subsequent 
yield of wheat. Mr. Hall points out that the winter months 
are one of the most critical periods in determining the 
yield of wheat. “ If the wheat be sown in October or early 
November it spends the next three or four months almost 
