MINERAL MATTERS RESTORED BY MANURE. 227 



are drawn, in large proportion, from the deeper layers of 

 the ground, where the roots of the cereals cannot pene- 

 trate. 



These fodder plants are consumed cither on the field 

 itself, as turnips in England, or in the stalls. A fraction 

 of the nutritive substances contained in these plants 

 remains in tlje body of the animals fed upon them, while 

 the remainder, ejected in the form of solid or liquid 

 excrements, constitutes farm-yard manure, the principal 

 bidk of which, however, consists of straw whicli has 

 served for litter. 



In Germany animals are not fed upon potatoes them- 

 selves, but upon the refuse from the distilleries of potato 

 spu-its, which contains all the nutritive substances taken 

 away from the soil in the potato crop, together with the 

 constituents of the barley-malt that have been used in the 

 process of mashing. 



Since tlie whole of the straw taken away in the crops 

 of the preceding rotation is, as a general rule, returned 

 to the arable soil in the shape of farm-yard manure, 

 the field is, at the outset of the new rotation, as rich as 

 before in the conditions for the production of straw ; 

 and there exists, under these circumstances, no ground 

 for a diminution of the straw-crops. 



With regard to the clover, turnips, potato-waste, &c., 

 upon which the stock on a farm is fed, there remains, as 

 already stated, in the bodies of the horses, cattle, &c., and 

 full-grown animals in general (which no longer materially 

 increase in weight), only a very small fraction of the con- 

 stituents of the food consumed ; but in the young cattle 

 sent to market, in the bodies of the sheep, in the milk 

 and cheese, a portion of these constituents is retained, 

 which is not returned to the soil in the farm-yard manure. 

 The loss of phosphoric acid and potash which the soil 



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