368 THE PRINCIPLES OF SOIL MANAGEMENT 



potash than is contained in a ton of average manure, 

 the use of this absorbent increases the fertilizing value 

 of the manure. It is, however, undesirable on some soils 

 to have a very large proportion of straw, on account 

 of its effect in retarding decomposition. 



Sawdust and shavings are sometimes used, but, 

 while they are good absorbents, they decompose very 

 slowly in the soil, making them objectionable on light 

 soils, and they have practically no plant-food materials. 

 Dry leaves absorb well, and decompose satisfactorily in 

 the soil. They do not add much fertility. 



237. Manures produced by different animals. There 

 is a great difference in the amount and value of manure 

 produced by different kinds of live stock. This is due to 

 a number of causes, among which are the size of the 

 animal, the nature of its food, and the mechanical con- 

 dition in which the digestive processes leave the solid 

 excrement. The differences affect not only the amount 

 of fertilizing constituents in the manures, but, what is of 

 more importance, they determine the nature and rapidity 

 of the decomposition processes, and hence affect the loss 

 of manurial substances and the value of the manure as a 

 fermentive agent in the soil. 



238. Horse manure. A well-fed, moderately worked 

 horse will produce from 45 to 55 pounds of excrement per 

 day, of which from 12 to 15 pounds consists of urine. 

 The straw used for bedding will amount to from 4 to 6 

 pounds. Roberts has computed the value of the excre- 

 ment to be nearly one-half the cost of the food, while 

 from Wolff's tables, based on a large number of determi- 

 nations in Europe, the combined solid and liquid excreta 



