Food for Plants. 



155 



each year just as much nitrogen as 8B, while 4B receives 

 more than two and one-half times as much as 8B. 



Data presented heretofore, and which are confirmed 

 by results hereafter to be presented, show that of the 

 four materials, nitrate of soda is' most effective in crop 

 production, that is, the crop is able to utilize or win 

 back a larger percentage of nitrogen in this form than 

 in any of the other forms. With a given amount of 

 nitrogen, therefore, the crop yield can be better main- 

 tained over a period of years by the use of nitrogen in 

 the form of nitrate of soda than in the other forms, pro- 

 vided the soil is one that does not allow rapid leaching. 



TABLE 1 



Yield of dry matter with different nitrogenous materials 



* Phosphoric acid, potash and lime, no nitrogen, 

 t First ten years. 

 t Second ten years. 



This apparently is what has happened in this case. 

 With the gradual exhaustion of soil nitrogen, which was 

 made availalile by the use of lime, and the failure of the 

 ammonium sulfate, blood and manure to give back in 

 the form of crops as large a proportion of the applied 

 nitrogen as the nitrate of soda, the yields with the for- 

 mer became gradually less. 



The fact that cylinder -I-B gave the largest average 

 yield through 20 years must not be taken as meaning 

 that the treatment given this cylinder is' necessarily the 



