130 



THE PRINCIPLES OF AGRICULTURE. 



considered. We should also take into account its ma- 

 nurial value, or value as a fertilizer. 



Any kind of food has a certain value as a fertilizer, 

 and may be used directly for that purpose if it is not 

 too expensive. 



Cotton-seed is extensively used in this way in the South. 



The manurial value, as in ordinary fertilizers, is de- 

 termined by the amount of nitrogen, phosphoric acid, 

 and potash contained. 



The following table shows the number of pounds of 

 the three substances contained in one ton of each variety 

 of food, and the manurial value of a ton. This value is, 

 of course, variable, depending upon the market value of 

 the three substances for the locality and the season. 



Manurial Substances in a Ton of Food, and their Value. 



