OXIDATION PROCESSES IN THE SOIL 



537 



of the organisms. Even nitrate formation in solution is greatly stimu- 

 lated by aeration. 74 



Deherain 75 found that when the moisture content of the soil is 5 per 

 cent the process of nitrate formation is very slight but it becomes 

 appreciable with 10 per cent moisture and reaches a maximum with 

 15 to 20 per cent. Schloesing and Mlintz 76 reported that nitrate forma- 

 tion in soil is at a maximum with the highest moisture content which 

 will not saturate the soil. When the soil approaches the saturation 



Fig. 37. Influence of crop upon nitrate content of the soil (after Lyon and 

 Bizzell). 



point, the process of nitrate formation is greatly reduced and may 

 disappear completely 77 (figure 36). The nature of the nitrogen source 

 was found to be important in this connection; the nitrogen in the 



74 Barthel, Chr. Bodenbakteriologische Untersuchungen. Centrbl. Bakt. 

 II, 25: 108-125. 1909. 



76 Deherain, 1902 (p. 793). 



76 Schloesing, Th., and Mlintz, A. Recherches sur la nitrification. Corapt. 

 Rend. Acad. Sci., 89: 1075. 1879. 



77 Traaen, A. E. tlber den Einflusz der Feuchtigkeit auf die Stickstoffum- 

 setzungen im Erdboden. Centrbl. Bakt. II, 46: 119-135. 1916. 



