RELATION OF DAIRYING TO SOIL 173 



on the roots of the clover and other legumes, 

 can and do make use of this "free" nitrogen of 

 the air. They take it and combine it with other 

 substances and store it up in these nodules in 

 much the same manner as the honey-bee stores up 

 his supply of honey for the time of need. The 

 clover plant then robs the nodules of their stored- 

 up nitrogen and incorporates it into its own 

 tissues. From the clover it is passed on to the 

 dairy cow, finds its way into the milk pail, serves 

 as food for pigs and calves, and is ultimately 

 returned again to the soil in the form of barn- 

 yard manure. Thus it will be seen that the 

 use of clover, alfalfa and other legumes actually 

 adds to the store of nitrogen in the soil, and the 

 dairy farmer, instead of exhausting the nitrogen 

 in his soil finds it, under his intelligent manage- 

 ment, continually improving. 



Other fertilizers necessary, however. It should 

 be mentioned in this connection, however, that 

 legumes do not add potash or phosphoric acid 

 to the soil, but like every other plant, remove 

 these substances. But since nitrogen is the sub- 

 stance soonest exhausted from almost every soil, 

 and since the legumes raised on the farm are 

 usually fed there, these plants may be said to 

 maintain the fertility of the soil. 



What system of dairying to follow. In deter- 

 mining upon the kind of dairying to be pursued, 



