74 



T. Lyttleton Lyon and James A. Bizzell 



ing an average figure for the percentage of mineral constituents would be 

 insignificant as compared with the differences in the quantities removed in 

 the crops. The percentages of phosphoric acid (P2O5) and potash (K2O) 

 given in the Yearbook of the Department of Agriculture for 1894 

 (pages 565 to 568) have been used. 



In Table 24 are given the relative quantities of nitrogen, phosphoric acid, 

 and potash removed in the maize and oat crops, and the relative nitrate 

 contents of the plats at the time of harvest or as near that date as is 

 practicable: 



TABLE 24. Relative Quantities of Nutrients Removed by Maize and Oats and 

 Relative Nitrate Contents of the Soil at Harvest 





1908 

 Maize 



1909 

 Oats 



1910 





Maize 



Oats 



Relative yields of 



Dry matter 



100 

 100 

 100 

 100 

 Sept. 17 

 100 



72 



71 



91 



176 



Aug. 7 



7 



100 

 100 

 100 

 100 

 Oct. 17 

 100 



755 



Nitrogen 



■ 828 



Phosphoric acid 



1,523 



Potash 



Dates of nitrate determinations 



1,265 

 Aug. 17 



Relative nitrate contents of soil 



34 







It will be noticed that in 1908 and 1909 the oat crop was small as com- 

 pared with the maize crop, while in 1910 it was relatively very large. In 

 both instances the nitrate content of the oat soil was characteristically 

 much lower than that of the maize soil. The characteristic relation of 

 nitrate content under oats and under maize appears to be independent 

 of the quantities of nutrients removed by the crops. 



The influence of alfalfa and of timothy on the production of 

 nitrates in soil 

 On the experiment field in which most of the experiments just described 

 were conducted, and consequently on similar soil, certain plats had been 

 seeded to alfalfa and contiguous plats to timothy in the spring of 1906. 

 These plats remained continuously in the same crops until the fall of 1911. 

 At the time when the seeding was done, part of the land planted to each of 



