126 SOME PRACTICAL LESSONS FROM SOIL BACTERIOLOGY. 



and utilized, only the roots and stubble being necessary for the in- 

 creased yield. 



The great lesson to be drawn from this subject is that, by means 

 of the nitrogen-fixing power of the legumes, aided by bacteria in 

 their roots, the farmer has a practical means of maintaining the 

 nitrogen content of his soil at a proper degree for high fertility. 

 There is no need of purchasing nitrate fertilizers. The money may be 

 better spent on phosphorus and potash. The cultivation of legumes 

 seems to be the secret of the continuance of agriculture, and if the 

 farmer will only learn the principles and acquire the habit of alter- 

 nating legumes with his other crops, he may maintain indefinitely 

 a high fertility in his soil, in spite of long-continued cultivation. 

 When in addition to this we remember the fact that the soil minerals 

 are being constantly dissolved in the soil waters, it becomes evident 

 that the farmer is by no means as dependent upon artificial fertilizers 

 as has been supposed. 



