272 PLANT BIOCHEMISTRY 



RATION OF THE ANIMAL. The compositioii and (|uantity of a given 

 animal manure vary with the kind, quantity, and digestibility of the 

 feed consumed. For examj^le, the digestibility of corn may exceed 90 

 j)er cent with the result that 10 per cent or less of the total quantity 

 consumed may be recovered in the manure. If overripe timothy hay, 

 which has a low degree of digestibility, is fed to animals, about two- 

 thirds of the total dry matter ingested may be excreted. 



KIND AND QUANTITY OF LITTER. The term Utter is applied to material 

 serving the double purpose of keeping animals clean and absorbing 

 the water-soluble fertilizer constituents. Many different materials have 

 been used for this purpose. These include cereal straws, cornstalks, 

 hays, wood shavings, sawdust, peat, and other materials which have 

 relatively high al)sorbcnt qualities. Wood products such as sawdust 

 anil shavings contain more lignins and resins than do straw, hay, and 

 cornstalks. These compounds are resistant to the action of micro- 

 organisms, and, as a result, wood products are decomposed slowly. 

 Straw, hay, and cornstalks contain a greater amount of readily decom- 

 posed carbohydrates, more protein, and more minerals than do wood 

 products. 



A substantial part of the components of a ration is changed by the 

 animal into products which differ from the original compounds. 

 Hence the composition of manure, as voided, differs from the com- 

 position of litter, although ration and litter may have a similar chemi- 

 cal analysis. Thus the ratio of litter to animal excreta will have an 

 important effect on the composition of manure. 



STORAGE OF MANURE. Conditions under which manure is stored have 

 a profound influence on its composition. Loss of maniuial con- 

 stituents may take place through two principal agencies: (1) leaching, 

 and (2) decomposition or fermentation. 



Since a large proportion of the total nitrogen and potassium of farm 

 manure is present in the form of soluble compounds, the possibility of 

 their loss through leaching is usually great. An adequate amoimt of 

 litter and tight floors prevent substantial losses from leaching in barns, 

 but exposure of poorly built heaps to rainfall favors losses of soluble 

 material. These losses are materially reduced if the heaps are built 

 with steeply sloped sides and placed on concrete floors. Storage of 

 manure in a roofed concrete pit will finther reduce losses from leach- 

 ing. 



Not only does manure contain relatively large quantities of soluble 

 compounds, but also other materials are present which can be changed 

 to soluble or volatile compounds as a result of decomposition or fer- 



