Relations of Higher Plants to the Formation of Nitrates 15 



Gauge No. 



Pounds per acre 



Nitric nitrogen in drainage water 



Nitrogen in manure used 



Nitrogen in maize crop, 1908 



Nitrogen in wheat crop, 1908-1909 



Nitrogen in maize crop, 1909 



Nitrogen estimated to have been in roots of the three 

 crops 



+261.5 



Net total . 



+261.5 



+51.1 

 —50.0 

 +49.0 

 + 7.9 

 +38.6 



+31.8 



+ 128.4 



+209.6 



+209.6 



+53.9 

 —50.0 

 +44.7 

 + 7.9 

 +31.2 



+27.9 



+ 115.6 



It thus appears that there is a smaller quantity of soluble nitrogen in the 

 cropped than in the fallow gauges, and that, either directly or indirectly, 

 the presence of the higher plant prevented the formation of nitrates. 



At Grignon it was found by Deherain (1902), as the result of experiments 

 with large vegetative tanks, that the loss of nitrogen in drainage water 

 from fallow soil amounted to 200 kilograms per hectare; from soil planted 

 to maize, harvested before maturity, the removal of nitrogen by the crop 

 plus that in the drainage water amounted to slightly less than that m the 

 drainage water from the fallow soil; from soil planted to oats the nitrogen 

 in the crop and in the drainage water amounted to only 63 kilograms per 

 hectare; and from soil continuously in grass the drainage water contained 

 almost no nitrogen. 



Deherain attributes this to the drying out of the soil by the growing 

 plants during the season most favorable to nitrate formation, except in 

 the case of maize, which was planted later. Leather (1912), who obtained 

 somewhat similar results, does not accept this explanation. 



The writers of this paper (1911) advanced the hypothesis that certain 

 higher plants exert a stimulating or a depressing influence on the proc- 

 ess of nitrate formation, dependmg on the stage of growth. Most of the 

 experiments cited above were performed before that time, and, since no 

 suggestion had previously been made as to any relation between higher 

 plants and nitrate formation, many data that might have thrown light 

 on that subject have probably been omitted from the publications. How- 

 ever, Leather, who published his results in 1912, has considered his data 

 with regard to this hypothesis and expresses himself as considering it a 

 possible explanation for the results obtained by Deherain and by himself. 



