Relations of Higher Plants to the Formation of Nitrates 97 



On September 8 careful notes were taken of the growth on each plat, and 

 a comparison was made not only between different plats but also between 

 the growth of millet on the previously planted sections and on the un- 

 planted section of each plat. 



In each plat the growth of millet was markedly better on the sections 

 that had been in crop during the previous year than on the unplanted 

 section. This applied to every crop in the experiment. A comparison of 

 the growth on the planted sections of the plats is given in Table 38, in 

 which the growth of millet on the plats planted to oats is taken as 100 and 

 the growth on the other plats is stated on this basis: 



TABLE 38. 



Growth of Millet on Plats Planted to Different Crops in the 

 Preceding Year 









Growth 





Growth 



Average 

 growth 

 of millet 



(per- 

 centage) 





Soil 

 treatment 



Plat 



of millet 

 (per- 



Plat 



of millet 

 (per- 









centage) 





centage) 



Maize 



f Not limed . . . 

 \ Limed 



3612 

 3G13 



37 



47 



3622 

 3623 



62 



71 



49 





59 



Potatoes 



1 Not limed . . . 



3614 



60 



3624 



81 



70 





\ Limed 



3615 



65 



3625 



88 



76 



Oats 



1 Not limed . . . 

 \ Limed 



3616 

 3617 



100 

 100 



3626 

 3627 



100 

 100 



100 





100 



It will be seen that the luxuriance of the growth of millet on these plats 

 was inversely proportional to the relative concentration of nitrates in the 

 soil. For instance, the millet made the best growth on the plats planted 

 to oats, and these plats had the lowest nitrate content. The poorest 

 growth of millet was on the maize plats, and these had the highest concen- 

 tration of nitrates. 



In Table 39 the relative nitrate content in the surface eight inches of 

 the several plats on June 28, which was only a few days before the millet 

 was planted, is compared with the percentage growth of millet on the 

 same plats: 



