Rotation of Crops. 
631 
greatly increased development of fibrous feeding root under the 
influence of the phosphatic manure. With the mixed manure, 
however, containing potash, there was about three times as 
much of it taken up as with superphosphate alone. But, with 
the supply of potash there was also a liberal supply of available 
nitrogen, to which the greatly increased growth is largely to 
be attributed ; and with the increased luxuriance much more 
potash was of course required if there were to be a correspond- 
ingly increased formation of the characteristic non-nitrogenous 
product of the cultivated root-sugar. Thus, we have — without 
manure only 4 to 6 lb. of potash taken up, with superphosphate 
(without potash) from 25 to 28 lb., and with the mixed manure, 
supplying besides phosphoric acid both nitrogen and potash, 
nearly 80 lb. of potash per acre per annum in the crops. 
Comparing the amounts of potash in the rotation crops with 
those in the continuously grown ones, it is seen that — without 
manure, and practically no growth, there was but little differ- 
ence in the amounts taken up ; with superphosphate there was 
little more than half as much taken up in the continuous as in 
the rotation crops ; whilst with the mixed manure, with full 
supply of potash, and much larger amounts of it in both the 
rotation and continuous crops, there was rather less than two- 
thirds as much in the continuous as in the rotation crops. 
The deficient amounts in the continuous crops are, however, as 
in the case of the other constituents, coincidents of the less 
amounts of produce of the continuous crops ; which, as has 
been pointed out, were, in the case of the superphosphate plot, 
due partly to the greater exhaustion of available nitrogen of the 
surface soil with the continuous growth, but partly also to the 
unfavourable mechanical condition of the soil induced by such 
growth ; and this was probably the chief cause of the deficient 
produce in the case of the mixed manure crops also. 
The Potash in the Barley Crops . — The second division of 
Table IX. records the results on this point. 
In the case of the turnips it was found that much more 
potash was accumulated in the roots than in the leaves ; and 
this fact was assumed to be connected with the greater amount 
of the carbohydrate — sugar— in the roots than in the leaves. 
The results relating to the barley show, however, that there 
was in every case more, and in some much more, potash in the 
straw than in the grain. On this point it is to be observed, 
not only that the root-crop is taken up when still in the 
vegetative stage, and its contents are still in the condition of 
reserve or migratory material, whilst in the case of the cereal 
the crop is ripened, and its constituents are, therefore, more 
