588 SOILS: PROPEETIES AND MANAGEMENT 



491. Heiden's formulas. — Perhaps a better and more 

 nearly accurate means of calculating the probable pro- 

 duction of manure is from the food consumed, rather 

 than from the combined weight of animals kept. Formu- 

 las have been devised from experimental data in Ger- 

 many and are designated as Heiden's formulas.^ From 

 the amount of absolute dry matter fed and the excrement 

 produced, Heiden was able to determine certain definite 

 relationships of the latter to the former. These, of course, 

 varied for different animals, being 2.10 for the horse, 3.80 

 for the cow, and 1.80 for sheep. For example, if a horse 

 received 20 pounds of dry matter daily, the manurial 

 production w^ould be 42 pounds. Such formulas are of 

 particular value on English farms, where the incoming 

 renter must pay the preceding tenant for the manure 

 produced on the farm during previous years. 



492. Poultry manure. — The excrement from poultry 

 is extremely variable, due to causes that have already 

 been discussed. In general, this manure is much richer 

 than that from other farm animals. Storer^ cites the 

 following analysis : — 



Composition of Poultry Manure 



Per cent 



Water 0.56 



Nitrogen 1.60 



Phosphoric acid 1.75 



Potash 0.90. 



Lime 2.25 



1 Henry, W. A. Feeds and Feeding, p. 265. Madison, 

 Wisconsin. 1904. 



2 Storer, F. H. Agriculture, Vol. 1, p. 613. New York. 

 1910. Also, Vorhees, E. B. Ground Bone and Miscellaneous 

 Samples. New Jersey Agr. Exp. Sta., Bui. 84. 1891. Also, 



