THE QUEST OF NITROGEN IOQ 



researches of Hellriegel and Wilfarth, who set forth with 

 a great array of facts the way in which nitrogen is ac- 

 cumulated and fixed in the soil. While there were in- 

 vestigators before this time who through study and 

 research had got an inkling of the true secret, they could 

 not find the key that unlocked it. Since the door was 

 opened by these agricultural wealth-makers an abun- 

 dance of evidence had accumulated, showing, without a 

 shadow of doubt, the manner in which the stores of free 

 nitrogen of the air are utilized in plant nutrition. 



The free nitrogen of the air, you know, is not available 

 plant food. No agricultural plant of itself can secure this 

 air element for its use not a wee bit of it. Of course, 

 many men, and some very learned men, at that, believed 

 in the early days just the opposite, but they have been 

 proven in the wrong, and at last the true solution of this 

 knotty problem has been found, and solved in a way of 

 the highest value to every man who manages land and 

 who employs the methods open to him, that his poor- 

 yielding fields may be restored to power, and their fer- 

 tility and that of others fully maintained in respect to 

 nitrogen. 



The story of the secret's discovery. To have the com- 

 plete story of the fixation of nitrogen, we shall have to go 

 back quite a good way in history ; back to the time when 

 chemistry first appeared as an exact science ; back to the 

 time when it was believed that all plant substances came 

 from the soil : we shall have to go back to these clays, in 

 order to know the early theories of plant nutrition. Only 

 the real guide-mark theories will be introduced, that the 

 development of the idea of nitrogen fixation in the soil 

 and its use by plants may be clearly understood. 



These important guide-mark theories are as follows: 



i. That all plant-food elements come from the soil. 



