Rotation of Crops. 
629 
was comparatively little more stored up in the grain, the excess 
for the most part remaining in the straw. The larger amount 
of total phosphoric acid taken up with the mixed manure than 
with superphosphate, the amount supplied by manure being the 
same in the two cases, is to be attributed to the coincident 
supply of other constituents in the mixed manure, inducing 
greater luxuriance, and with it greater activity of collection. 
The Amounts of Potash in the Rotation , and in the Continuous 
Crops. 
The results relating to the amount and distribution of potash 
in the rotation and in the continuous crops are recorded in 
Table IX. 
The Potash in the Root-crops. — Before referring to the details 
on this point, attention should be recalled to the facts fully 
illustrated in other papers — that root-crops are essentially 
sugar crops ; that the very characteristic effect which nitro- 
genous manures exert on their increased growth is mainly 
represented by a greatly increased production of the non- 
nitrogenous substance — sugar ; that, however the action is to 
be explained, it is certain that the presence of potash is an 
important condition of the formation in plants of carbohydrates 
generally ; and that, in the case of root-crops, the production of 
the carbohydrate — sugar — is greatly dependent on a liberal 
available supply of potash. 
Referring to the upper division of the Table, and for the 
purpose of the first illustrations to the rotation results, it is seen 
that, without manure and very abnormally small crops, there 
were only three, four, or five, times as much potash in the roots 
as in the leaves ; with superphosphate, on the other hand, and 
greatly increased root development, there were eight or nine 
times as much potash in the roots as in the leaves ; and with 
the mixed manure (including potash), there were, with the 
further greatly increased actual amount of roots and of potash 
in them, seven or eight times as much in the roots as in the 
leaves. That is, there was the greatest accumulation of 
potash with the greatest accumulation of sugar. 
Looking to the actual amounts of potash in the total 
produce, roots and leaves together, of the rotation crops, it is 
seen that, without manure there was only from 4 to 6 lb. of 
potash per acre per annum ; but with superphosphate, without 
potash supply, from 25 to 28 lb. That is, without any supply 
by manure the plants were able to gather about 20 lb. more 
potash per acre per annum from the soil itself, by virtue of the 
