260 FARM MANURE 



so that what plant food they do contain becomes available 

 to a very slight extent. But sawdust and shavings are good 

 absorbers of liquid, even better than straw, and are con- 

 sequently of considerable value. They do no harm in the 

 soil as is sometimes claimed. 



197. Mixed Excrement. — Considering the mixture of solid 

 and liquid excrement, exclusive of litter, it is found that 

 the composition varies with the age of the animal and the 

 kind of food eaten. An adult animal, working or fattening, 

 retains not more than 5 or 10 per cent, of the nitrogen, 

 phosphoric acid, and potash in the food. Cows giving 

 milk, and young animals, retain from 25 to 50 per cent, of 

 these constituents in their food. Taking the average excre- 

 ment produced on the farm, it may be said to contain 

 about 80 per cent, of the fertilizing constituents of the 

 food eaten. 



The kind of food eaten will influence the composition 

 of excrement. If the food consists of press cake, grains, 

 bran, or other concentrated material, the excrement will 

 be much higher in nitrogen, phosphoric acid, and potash 

 than if the food were roughage, or ensilage, or beets (see 

 Table III). 



198. Farm Manure. — This product, as mentioned at the 

 beginning of the chapter, is a mixture of solid excrement, 

 liquid excrement, and litter. As can be readily seen from 

 what has been said about the causes of variation in the 

 composition of excrement, and what is known about variation 

 in the composition of litters, the amount of plant food in 

 farm manure is never constant. From the discussion which 

 follows as to the decomposition and losses of manure piles, 

 it is to be noted that these factors also affect the com- 

 position. For purposes of rough calculation, however, it is 

 somewhat generally agreed that the average farm manure 

 contains about 0.5 per cent, nitrogen, 0.25 per cent, phos- 

 phoric acid, and 0.5 per cent, potash; or, to put it more 

 plainly, a ton of farm manure contains 10 pounds of nitrogen, 

 5 pounds of phosphoric acid, and 10 pounds of potash. 



199. Compounds in Fresh Farm Manure. — When first 

 produced, farm manure contains in the solid excrement, 



