274 FEEDS AND FEEDING 



Farm manures teem with bacteria of various kinds which cause 

 chemical changes not only in the manure but also in the soil itself, con- 

 verting insoluble plant food into forms available for crop growth. 



After much practical work at the Ohio Station, Thorne 1 concludes 

 that the fertilizing constituents of farm manures have as high a value per 

 pound as those in such high-grade fertilizers as tankage, bone meal, and 

 muriate of potash. In view of the highly beneficial effects which farm 

 manure has in addition to supplying nitrogen, phosphoric acid, and 

 potash, this is a conservative estimate. Previous to the World "War the 

 price of the fertilizing constituents in commercial fertilizers was about 

 as follows : nitrogen 18, phosphoric acid 4.5, and potash 5 cents per pound. 

 Tho the prices of fertilizers have now declined materially from war-time 

 levels, at present the fertilizing constituents can not be secured at retail 

 in high-grade fertilizers for less than approximately the following 

 amounts: nitrogen 20, phosphoric acid 7, and potash 7 cents per 

 pound. These values are accordingly used in this volume in computing 

 the fertilizing value of feeding stuffs and the manure resulting from 

 feeding them to farm animals. 



433. Fertilizing constituents recovered in manure. The proportion 

 which is recovered in the manure of the total nitrogen, phosphoric acid, 

 and potash supplied in the feed depends on the age and kind of animal, 

 as shown in the following table from Warington : 2 



Proportion of nitrogen and ash of food which is voided by animal 



Nitrogen Ash 



Per ct. Per ct. 



Horse at work 100.0 100.0 



Fattening ox 96. 1 97.7 



Fattening sheep 95.7 96.2 



Fattening pig 85 .3 96.0 



Milk cow 75 .5 89 . 7 



Calf, fed milk 30.7 45.7 



The mature horse at work is merely repairing his body tissues as 

 they are broken down. (140) Therefore no nitrogen or ash (containing 

 the phosphoric acid and potash) is stored in his body, but all the 

 nitrogen and practically all of the ash are voided in the manure. (A 

 negligible amount of ash is excreted in the perspiration.) With fatten- 

 ing animals whose bodies are nearly or quite mature, but little of the 

 fertilizing constituents supplied in the food are retained in the body, 

 over 95 per ct. of both nitrogen and ash being voided by the fattening 

 ox and sheep. (123) With the pig fattened while not yet mature and 

 storing nitrogen in his lean-meat tissues, about 85 per ct. of the nitrogen 

 of the food is returned in the manure. As milk is rich in nitrogen and 

 ash, the cow in milk voids only about 75 per ct. of the nitrogen and 89 

 per ct. of the ash contained in her food. (149) The young calf, growing 

 rapidly in bone, muscle, and body organs, voids only 30.7 per ct. of the 



1 Ohio Bui. 183. a Chemistry of the Farm, p. 214. 



