CHAPTER IX. 



GROUND KAPE-CAKE. 



Nature and composition of; the diffusibility of its constituents in the Boll is com- 

 paratively great Its importance as a manuring agent is small The Saxon 

 agricultural experiments with rape-cake The inferences from them. 



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

 tion of the iatty 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 incombusti- 

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

 seed ash consists of phosphates, and differs but little in 

 composition from the ash of the grain of rye ; phos- 

 phates of the alkalies and phosphates of magnesia pre- 

 dominate in it. There is no great error made in assum- 

 ing that in 100 Ibs. of rape-cake a field receives the same 

 amount of the incombustible constituents of rye grain 

 as is contained in 250 to 300 Ibs. of the latter. . 



The azotised matter in rape-cake powder is slightly 

 soluble in water, but its solubility increases with inci- 

 pient putrefaction ; hence the nutritive matters con- 

 tained 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 dissolved, by the earth particles that come in 

 contact with them. Whereas with rape-cake powder 

 this takes place only after its azotised matter has been 

 completely decomposed, and its nitrogen converted 

 into ammonia. This decomposition proceeds, however, 



