76 



exposed soils lose by oxidation and decomposition a large 

 proportion of tlieir organic constituents. 



To make good the losses occasioned under the several con- 

 ditions above enumerated, there is a constant demand for 

 fresh supplies of fertilizing materials for the purpose of 

 returning to the soil the elements of plant food which have 

 been removed, and these elements may be returned, in part, 

 either in the form of some portion of the crop which has 

 been produced, or by the application of supplies of manures 

 derived from the feeding of the crops in question to farm 

 animals. 



It is the design of this bulletin, therefore, to furnish some 

 practical information with regard to the methods of utiliz- 

 ing to the best advantage crude domestic manures, in con- 

 junction with appropriate kinds and quantities of commer- 

 cial fertilizers. 



It is consequently not strictly wathin the province or 

 scope of this pamphlet to treat of the methods of prevent- 

 ing or avoiding the other forms of soil exhaustion above re- 

 ferred to (viz : by washing and exposure), but the employ- 

 ment of better systems of drainage and the protection of the 

 land by keeping it covered as continuously as possible with 

 some vegetable growth, even if that growth be only grass, 

 will be found to prove valuable aids in the diminution of 

 the losses due to these sources. 



Of the dozen or more elements which the soil supplies 

 under ordinary conditions for the development and mainte- 

 nance of plant life, all except three are commonly present 

 in soils in sufficient quantities to meet the requirements of 

 plant growth. These three important constituents of plant 

 food are nitrogen, potash and phosphoric acid, and it is 

 these three substances which both artificial fertilizers and 

 domestic manures are designed to supply to the soil. 



Manures are commonly divided into two classes — viz : 

 stimulant and nutritive manures. 



