206 SYSTEMS OF PERMANENT AGRICULTURE 



As a general average for dairy fanning, cattle feeding, and sheep 

 feeding, it is shown that practically one third of the organic matter, 

 three fourths of the nitrogen, and three fourths of the phosphorus 

 contained in the feed and bedding are recovered in the total 

 manures. Nearly all of the potassium may be recovered except 

 that sold in milk. (Some potassium may be excreted through the 

 skin, especially in hot weather, but even this is washed off in the 

 pastures by summer rains.) 



Emmet and Grindley have reported the following suggestive 

 data from digestion experiments with swine (Journal American 

 Chemical Society (1909), 31, 577): 



COEFFICIENTS OF DIGESTIBILITY OF THE CONSTITUENTS IN THE FEEDS 



CONSUMED 

 Per Cent Digested 



It is common knowledge among farmers that swine fed largely 

 on grain produce but little solid manure; and in these experiments 

 only about 13 per cent of the organic matter, 20 per cent of the 

 nitrogen, and 30 per cent of the phosphorus were recovered in the 

 solid excrement. However, the existing data are not sufficient to 

 justify the adoption of these determinations as representing the 

 average digestibility by swine of the phosphorus contained in the 

 grain rations. That the normal coefficient is high, is evidenced by 

 the fact that, unlike most animals, swine normally excrete very 

 appreciable amounts of phosphorus in the urine. 



The production, composition, care, and value of farm manure are 

 discussed in a later chapter. 



