COMPOSITION OF MANGOLDS 115 



dung year after year on the same land, lend no colour to the 

 opinion that in ordinary farming there is likely to be serious 

 loss of nitrogen by "denitrification "* when nitrogenous manures 

 and dung are used together. The soil is probably always 

 suffering losses of nitrogen in the gaseous state through various 

 bacterial changes, and these losses will increase the higher 

 the condition of the land becomes and the more nitrogenous 

 bodies of an easily decomposable nature are present. But 

 there is no evidence in the Rothamsted mangold experiments 

 to support the view that specific and excessive loss will set 

 in when dung and nitrate of soda, or other active nitrogenous 

 manure, are used together. 



G. The Composition of the Mangold Crop as affected by 

 Manuring. In many of the years during which the mangolds 

 have been grown, determinations have been made of the 

 amount of sugar contained in the roots from the different 

 plots, sugar being the chief constituent of the dry matter of 

 the mangold and the main element in its value as food. Table 

 XLIII. gives a summary of the results obtained in 1900 and 

 1902, years when crops were obtained above the average both 

 in regularity and magnitude. In the various columns are set 

 out the average weight of the roots, the proportions of dry 

 matter and of sugar, both the glucose or reducing sugar and 

 the more important cane sugar, also the dry matter and sugar 

 in pounds per acre on each plot. Other columns give the 

 quotient of purity, by which is meant the percentage of cane 

 sugar in the dry matter, and the glucose coefficient or the 

 relation per cent, of the glucose to the cane sugar. 



It will be at once seen that the variations in the composi- 

 tion of the roots are small compared with the variations in the 

 yield from plot to plot; the average weight of root varies 

 from 071 to 3 '95 lb., but the proportion of dry matter only 

 fluctuates between 15 '3 per cent, and 10*9 per cent. In the 

 main the root grows as a whole from a very early stage, 

 increasing in size but maintaining a fairly uniform composition. 



* See p. 219. 



