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Relations of Higher Plants to the Formation of Nitrates 35 



TABLE 9. Nitrates in Maize and in Unplanted Sections of Plat3 1, 4, 7, 10, 13, in 



1907 (Parts per Million) 





August 5 



August 19 



August 25 



September 16 



Plat 



Maize 



Un- 

 planted 



Maize 



Un- 

 planted 



Maize 



Un- 

 planted 



Maize 



Un- 

 planted 



1 



4 



7 



10 



13 



52 

 49 

 63 

 24 

 18 



90 

 HI 

 96 

 73 

 56 



19 

 16 

 9 

 14 

 30 



72 

 84 

 54 

 50 

 79 



15 

 16 

 10 

 31 

 41 



70 

 92 

 80 

 69 

 69 



13 

 15 

 36 

 31 

 55 



130 

 208 

 143 

 165 

 183 



Average 



41 



85 



18 



68 



23 



76 



30 



166 



there was only .73 inch between August 1 and August 31. On September 

 9 there was a rainfall of 1.06 inch; however, although this soil is very- 

 sandy, there could have been little leaching of nitrates judging from the 

 nitrate content on September 16. 



Notwithstanding the very favorable conditions for nitrification and 

 the large nitrate content of the unplanted soil, there is practically no 

 increase of nitrates in the planted soil. This is a striking exemplification 

 of the hypothesis previously advanced, namely, that at least certain 

 plants in some way inhibit the formation of nitrates in the soil during 

 the later stages of plant growth. It is certainly impossible to account 

 for the failure of the nitrates on the cropped soil to increase by sup- 

 posing that they were leached out of the topsoil, as they would not have 

 remained practically constant while the nitrates in the uncropped soil 

 doubled. 



The plats sown to millet and to soy beans afford an opportunity to study 

 the effect of these crops on the nitrate content of the soil by comparing 

 the ends of the plats which, as alreadj^ explained, were sown to either 

 millet or soy beans alone, with the unplanted ends of contiguous plats. 

 Such a comparison is made in Table 10. 



There seems to be little tendency for the nitrates to increase under 

 either of these crops during the early stages of growth; yet those crops 

 that were planted after the first analysis was made, thus permitting 

 frequent observation, display something of this tendency. Thus, on 



