On the Significance of the Nitrates Contained in 

 Plants for Animals and Men, 



BY 



T. Ishizuka, Nogakus/ri. 



As the presence of nitrates in the food is of more influence 

 upon the well-being of animals and men than is often supposed, it 

 is well to discuss such circumstances as relate to the amount of 

 stored up nitrates in plants ; these are principally : 



a) . Intensity of nitrification in the soil. 



b) . The amount of rain removing the nitrates from the soil. 

 The amount of nitrates formed in the soil depends, of course, 



above all upon the amount of ammonia present ; in the second 

 place upon the condition of the soil. 



Defifrain noticed a great influence of the kind of soil upon 

 the intensity of nitrification : a porous soil formed more than 

 double as much of nitrate as a less porous one ; a clayey soil 

 would admit less aeration, therefore would be also less favourable 

 for nitrification (Ann. Agronom. 21, 353, 1895). 



In the third place the development of the microbes of nitri- 

 fication (Nitrosomonas and Nitromonas) depend not only upon 

 climate, and mechanical condition of the soil, but also upon the 

 presence of certain chemical compounds ; thus it was found by 

 Dumont that the increase of potassium salts in a soil and the 

 simultaneous presence of humus and calcium carbonate favour 

 the development of the nitrifying microbes, and therefore the 

 production of nitrites from ammonia which very soon pass into 

 nitrates in the soil. 



Furthermore, the amount of rain must have a great influence 

 upon the amount of nitrates, as_ these are not absorbed by the 

 soil. Heavy rains combined with thorough drainage of the field 

 therefore deprive the soil well nigh completely of the nitrates 

 present. On the other hand, frequent small showers will merely 

 promote the energy of nitrification, and a larger amount of 

 nitrates will accumulate, because of the rain water in this case 

 not draining away, but simply evaporating- again from the soil. 



