ENERGY AND NITROGEN TRANSFORMATION 



509 



would repress nitrate formation in the soil. Nitrification was found 6 

 to be checked when the carbon-nitrogen ratio in the soil is 13-15 to 1, 

 but not when the ratio is 11-11.6 to 1. When molasses was added to 

 the soil, nitrification was stopped when the ratio was about 11:1, but 

 was not injured when the ratio was less. However, the addition of 

 carbon sources not readily available, such as butyric acid and alcohol, 

 did not injure nitrification at a ratio of 14:1, but did injure it at a higher 

 ratio. This phenomenon is brought out clearly when cellulose is added 

 to the soil. The organisms using the cellulose as a source of energy 

 assimilate the soil nitrates, without injuring, however, the activities 



So 

 o 



u 

 o 



K) 



u 



"30 

 Z 



< 



< 



Number or ZiAys at "Room Te m vehatu'f.e 

 / 2 3 4 'S lo 7 



1 r' 1 1 1 1 1 j 



Dw iedBlood Useltd= iSS M$S- M. No 2)exmos,£. 



,, ,, ,, T 4^,5- ,, .■> 3o ,, >> 



Fig. 30. Influence of glucose on ammonia accumulation from dried blood added 

 to soil (after Lipman and associates). 



of the nitrifying bacteria. Only after all the celluloses have decom- 

 posed, do nitrates begin to accumulate again, as shown in fig. 31. 



As long as there is free available energy, in excess of the available 

 nutrients, there will be only a minimum accumulation of available 

 plant food. When the energy approaches exhaustion the nutrients 

 begin to accumulate, as shown in table 47. 7 



6 Clark, H. W., and Adams, G. O. The influence of carbon upon nitrification. 

 Jour. lnd. Engin. Chem., 4: 272-274. 1912. 



7 Waksman, S. A. The influence of available carbohydrates upon ammonia 

 accumulation by microorganisms. Jour. Amer. Chem. Soc, 39: 1503-1512 

 1917. 



