Stable Manures and vSoil FtMtilitv 



311 



300 



manured 



1880 1890 1900 1910 1920 

 Fig. 124. Influence of manures upon the conservation of soil fertility (from 



Russell ) . 



Table 68. Manure Spread ox Field Compared wnn Manure Left in Piles 

 (from Salter and Schollenberger) 



Relative Value 

 in Increasing 

 Crop Yields 

 100 



71 



80 



Manure spread and plowed under immediately 



Manure spread 2 days before plowing 



Manure in piles 2 days before spreading and plowing 



Manure spread 14 days before plowing 



Manure in piles 14 days before spreading and plowing 



49 

 55 



residual effect of manure in building up the humus content of the 

 soil (Table 68). 



Effect of Stable Manures upon Plant Growth and Soil Fertility 



The important role of stable manures in plant growth and in soil 

 fertility has been variously ascribed to six distinct factors: (1) Ma- 



