118 EXPERIMENTS UPON ROOT-CROPS 



potash ; but this effect of potash in inducing the ripening of 

 the mangel is not visible in the dunged plots. 



Although the analyses which have been made of the nitro- 

 genous constituents of mangels are not yet wholly satisfactory, 

 certain results are apparent. 



As regards the total nitrogen, the proportion present in 

 the root reflects the supply of nitrogen in the manure, and 

 as the roots get larger and more watery with the use of 

 nitrate of soda or any excess of nitrogenous manure, so 

 also does the proportion of nitrogen rise in the substance of 

 the root. As to the forms in which the nitrogen is combined : 

 the proportion of nitrogen in the proteid condition, whether 

 soluble or insoluble, is at its highest in the plants which 

 are nitrogen starved, and falls to its lowest point where 

 nitrate of soda or any excess of other nitrogenous manures 

 are used. 



The amides are also at their highest on the plots which 

 show immaturity because of the use of large quantities of 

 nitrogen, and especially of nitrate of soda ; on the contrary, 

 the use of potash at once diminishes the proportion of 

 amides. The proportion of nitrates present is less affected 

 by the manuring, but it is highest when an excessive amount 

 of nitrogenous manure is used, or when nitrate of soda supplies 

 the nitrogen in the manure, and is usually diminished by the 

 use of a free supply of potash. 



Speaking generally, then, it will be seen that though the 

 composition of mangels is not greatly influenced by manuring, 

 yet certain factors go together. Highly nitrogenous manure, 

 especially when the nitrogen is in the form of nitrate of soda, 

 produce large and watery roots, whose immaturity is reflected 

 in the low quotient of purity, the high glucose coefficient, the 

 high content of nitrogenous matters, of Avhich again a large 

 proportion is in the form of amides and nitrates. If the 

 nitrogen is in excess and the mineral manures are deficient 

 these differences are intensified, whereas an abundant supply 

 of potash tends to produce a more normal root. 



