62 6 
Rotation of Crops. 
crops with those in the continuous ones, the equally small, or 
even smaller, amount taken up without manure by the latter, 
is further confirmation of the incapability of this assumed 
restorative crop to yield any practical amount of produce with- 
out adequate soil supplies. With superphosphate alone, as 
also with the mixed manure, the continuous crops took up 
little more than half as much phosphoric acid as the rotation 
ones under the assumed fairly parallel conditions as to manu- 
ring. The deficiency is, however, obviously not due to any 
deficiency of supply within the soil, but is only a coincident of 
the less total growth, attributable to a great extent, as has been 
explained, to the unfavourable mechanical condition of the soil 
induced by the continuous growth of the crop. 
Lastly in regard to the phosphoric acid in the turnip crops, 
it is to be observed that in all cases much more was accumu- 
lated in the edible roots than in the loaves which remain only 
for manure again ; indeed, in the case of the most normal 
crops, those grown in rotation with the full mixed manure, 
there was five or six times as much accumulated in the roots as 
in the leaves. 
The Phosphoric Acid in the Barley Crops . — Looking first to 
the amounts in the total produce, grain and straw together, 
and to the portions of the rotation plots from which the previous 
root-crops had been removed, it is seen that, without manure, 
rather more than 13 lb. of phosphoric acid was, on the average, 
annually removed in the barley crops ; and where superphosphate 
had previously been applied for the roots, the succeeding barley 
took up only about 14 lb., that is scarcely any more than with- 
out the supply of it ; but where the mixed manure, including 
nitrogen, had been applied for the roots, there was about one- 
and-a-lialf time as much, or rather over 21 lb. of phosphoric acid 
in the succeeding barley crops. Then, where the root-crops had 
not been removed from the land, the amounts of phosphoric 
acid in the succeeding barley crops were, without manure, about 
12 lb. per acre, with superphosphate about 18 lb., and with the 
mixed manure nearly 25 lb. In the case of the phosphoric acid, 
therefore, as in that of the nitrogen, the influence of the manu- 
ring, and other treatment, of the preceding crop of the course, 
is clearly reflected in the amounts taken up in the succeeding 
barley. 
Comparing the amounts of phosphoric acid in the rotation 
barley crops with those in the continuously grown ones, it is 
seen that, both without manure and with superphosphate, the 
rotation crops took up considerably the most phosphoric acid ; 
and this was the case notwithstanding that the continuously 
