618 
Rotation of Crops. 
gen taken up than without manure ; in fact, when grown in 
rotation from three to four times as much, and when grown con- 
tinuously more than twice as much. There was, too, very much 
more in the rotation than in the continuous crops. The detailed 
results published elsewhere, relating to the continuous growth of 
root-crops afford conclusive evidence that the increased amount 
of nitrogen taken up by the crop under the influence of phos- 
phatic manures is derived from the resources of the soil itself, 
by the aid of the greatly enhanced development of fibrous feed- 
ing root induced by such manures. 
With the mixed manure containing nitrogen there was, as 
with superphosphate alone, much more nitrogen taken up under 
rotation than with continuous growth. But, under rotation, 
there was about twice as much taken up with the mixed manure 
containing nitrogen as with superphosphate without nitrogen ; 
and with continuous growth there was nearly three times 
as much taken up as with superphosphate without nitrogen. 
It is clear, therefore, that the crops, whether grown in rotation 
or continuously, took up much of the nitrogen supplied by the 
manure. Indeed, it cannot be doubted that, beyond the small 
amount of combined nitrogen annually coming down from the 
atmosphere in rain and the minor aqueous deposits, the source 
of the large amount of nitrogen of root-crops is the store of it 
within the soil, whether this be due to accumulations, or to direct 
supply by manure. On the other hand, the large amounts of 
produce obtained by the aid of nitrogenous manures on land to 
which no carbonaceous manure has been applied for about fifty 
years is evidence that the atmosphere is at any rate the chief, 
if not the exclusive, source of the carbon of the crops. 
Lastly, as to the results in the Table relating to the Swedish 
turnips, it is seen that by far the greater part of the nitrogen of 
the crops was accumulated in the edible root. 
The Nitrogen in the Barley Crops . — The second division of 
Table YI. shows the average amounts of nitrogen per acre per 
annum over the eight years in the rotation and in the continuous 
barley crops respectively. 
Referring to the results chiefly in their bearing on the ques- 
tion of the position of the barley crop in rotation, and of its de- 
pendence, or otherwise, on the soil for its supplies of nitrogen, 
the amounts of it in the total crops, grain and straw together, 
are of most interest. 
When considering similar results relating to the first crop of 
the course — the Swedish turnips, it was seen that the average 
amount of nitrogen per acre per annum in the total crops, roots, 
and leaves together, was only 10 or 11 lb., or even less, when 
