282 



CHAPTEE IX. 



GEOUXD RAPE-CAKE. 



Nature and composition of ; the diffusibility of its constituents in tlie soil is 

 comparatively great — Its importance as a manui-ing agent is small — 

 The Saxon agiicultural experiments with rape-caie — The inferences from 

 them. 



THE residuary mass left by rape-seed after the extrac- 

 tion of the fatty oil from it by the press, contains a 

 large proportion of a matter abounding in nitrogen, 

 which is nearly related to the casein in milk. In addi- 

 tion to this substance, it contains the same incombustible 

 or ash-constituents as the ashes of seeds. The rape-seed 

 ash consists of phosphates, and differs but httle in com- 

 position fi'ora the ash of the grain of rye ; phosphates of 

 the alkahes and phosphate of magnesia predominate in it. 

 There is no great error made in assuming that in 100 lbs. 

 of rape-cake a field receives the same amount of the 

 incombustible constituents of rye gram as is contained in 

 250 to 300 lbs. of the latter. 



The azotised matter in rape-cake powder is shghtly 

 soluble in water, but its solubihty increases with inci- 

 pient putrefaction ; hence the nutritive matters contained 

 in it are much more widely diffused in the ground than, 

 for instance, the principal ingredients of guano, ammonia, 

 and phosphoric acid, which are absorbed, as soon as dis- 

 solved, by the earth particles that come in contact with 

 them. Wliereas with rape-cake powder this takes place 



