CoMrosri'ioN oi' M \N(;i:i.s iis 



opinion that in oniinary tarniing there is likoly to be serit)U.s 

 loss ofnitrogen by " denitrihcation " ^ whtMi iiit ro^onous manures 

 and dung are used together. Tiie soil is undoubtedly alwuys 

 suffering losses of nitrogen in the gaseous state through various 

 bacterial changes which can be roughly grouped togetlier 

 under the term "denitritication," and these losses will increase 

 the higher the condition of the land becomes and the more 

 nitrogenous bodies of an easily decomposable naturi' are 

 present. But there is no evidence in the Kothamsted mangel 

 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. T/te Composition of the Mangel Crop as ajcrtrti hi; 

 Manuring. In many of the years during which the mangels 

 have been grown, determinations have been made of the 

 amount of sugar contained in the roots from tlie ditterent 

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

 the mangel and the main element in its value as food. Tal)le 

 XLIII. gives a summary of the results obtained in 1000 and 

 1902, years when crops were obtained above the average both 

 in regularity and magnitude. In the various ct)lunms are set 

 out the average weight of the roots, the prt)portions of dry 

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

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

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

 <luotient of purity, by which is meant the percentage of lanc 

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

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



It will be at once seen that the variations in the eompo>i- 

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

 yiehl i'vom plot to ph^t ; the average weight of root varir> 

 from 071 to 305 lb., but the pr()])ortion of dry malt.r ohIn 

 fluctuates between 153 per cent, and lol> per (rnt. In ilif 

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

 increasing in size but maintaining a fairly uniform coniposition. 



♦ Seep. 219. 



