WITH VARIOUS NITROGENOUS MANURES 77 



during the warmer portion of the year when nitrification is 

 active, renders such a surface accumulation of nitrogen as 

 readily available to the plant as the nitrate of soda itself. 



On the completely manured plots the rape cake, 4 C, is 



60OO Ib 



Plot 10 40. 4 A. 4AA. 



Unmanured Minerals Minerals Minerals 



only. +43 ib.N. +43IB.N. 



as Ammonia. as Nitrate. 



AC. 7-2 



Minerals Farmyard 



+49 I b. N. Manure 

 as Rape Cake. 



Grain per Acre', I b. 



Straw per Acre, Ib 



FIG. 11. Yield of Barley (Grain and Straw) with different sources 



of Nitrogen. Averages for 51 years, 1852-1902. 

 The figures in the labels indicate bushels of grain and cwt of straw. 



not quite so effective as the more active forms of nitrogen, 

 giving over- the whole period an average yield of 41 against 

 43*5 and 421 bushels of grain. This small deficiency has 

 not diminished in the later years, which seems to indicate 

 that the nitrogen compounds of rape cake are almost wholly 

 utilisable by the crop to which they are applied. At any rate, 



