166 FIRST PRINCIPLES OF AGRICULTURE. 



Fertility in Feeds A fodder or feed has a fertiliz- 

 ing value by virtue of the manurial constituents — nitro- 

 gen, phosphoric acid, and potash — contained in it. Com, 

 oats, hay, wheat, or other crops, when sold from the 

 farm, carry with them a certain portion of these con- 

 stituents ; and the sale of these products continued for a 

 long time must result in the exhaustion of the soil. If 

 they are returned to the land in whole or in part, they 

 will aid in the growth of other plants, and the time of 

 exhaustion is postponed. 



The Relative Fertility of Fodders and Feeds. — 

 Fodders are much less valuable as direct manures than 

 the feeds, — first, because they contain less of the essential 

 constituents ; and second, because, from their woody char- 

 acter, their decay is less rapid, though both are valuable 

 as indirect manures, because of their high content of or- 

 ganic vegetable matter. The direct fertilizing value of a 

 feed is largely measured by its content of nitrogen ; though 

 the ash constituents, phosphoric acid and potash, are also 

 of considerable importance. 



Mill-Feeds vs. Commercial Fertilizers Fine- 

 ground mill-feeds, though less concentrated, are quite 

 as good sources of available organic nitrogen as the best 

 commercial forms furnishing that element ; the phosphoric 

 acid is less valuable than when contained in forms com- 

 pletely soluble in water, because decay must take place 

 before it becomes available to the plant ; while the potash, 

 which is largely soluble in water, is regarded as equiva- 

 lent in value to that contained in forms free from muri- 

 ates. Of all the feeds we have, cottonseed meaJ is the 

 richest in fertilizing constituents. In the Southern States 



