362 J otirnal of Agricultural Research voi.x, no. 7 



DISCUSSION OF RESULTS 



To what is this very marked efifect of paraffin upon the accumulation 

 of ammonia and nitrate nitrogen to be ascribed? Where the major 

 differences are observed, the evidence does not seem to support the view 

 that it is an inhibitory effect exerted upon the ammonifying and nitri- 

 fying organisms. There is evidence that such an effect may occur to a 

 slight extent in some instances, but the very large actual disappearance 

 of nitrate and ammonia nitrogen, one time present, certainly can not be 

 ascribed to such a phenomenon. Since the experimental conditions 

 were strictly aerobic, as the nitrification in controls and sometimes in 

 treated samples will show, they would tend to eliminate denitrifying 

 processes. The only other possibility hes in an actual metabolic con- 

 sumption by organisms stimulated by the presence of paraffin. It is 

 rather difficult to conceive of the consumption of such large quantities 

 in this manner in such a short period of time, unless one has observed 

 such cultures. 



Parallel with the disappearance of active nitrogen, there has also been 

 a disappearance of paraffin and an enormous development of certain 

 species of fungi. This growth of saprophytic fungi was so abundant 

 where ammonium sulphate and cottonseed meal were added that at the 

 end of two to four weeks the cultures appeared to be almost solid masses 

 of white hyphae which later developed almost all varieties of color. In 

 the absence of added nitrogen, while the growth was not sufficient to be 

 macroscopically visible, other physical characteristics showed growth to 

 be abundant. 



Rahn (6) a number of years ago called attention to the presence in 

 soil of a species of Penicillium capable of utilizing paraffin in its metabol- 

 ism when grown in cultural solutions containing paraffin as the only 

 organic constituent. Later Sohngen (7) isolated and studied from soils 

 and other sources a number of species of bacteria capable of utilizing 

 paraffin under similar conditions. It is not unreasonable, therefore, to 

 assume that the enormous growth of fungi observed where paraffin was 

 added utilized this as a source of carbon and energy; also that the active 

 nitrogen observed to disappear was used as source of nitrogen in the 

 metabolism of the fungi. Where no nitrogen was added, available nitro- 

 gen soon became the limiting factor in fungus growth. Growth under 

 such conditions was accordingly much more Umited. So long as nitro- 

 gen remained the limiting factor in growth, that present in a form capa- 

 ble of being utilized was consumed as rapidly as it became available. 

 Ammonia and nitrate nitrogen are both readily available to many sapro- 

 phytic bacteria and fungi; hence, the quantities of these two forms of 

 nitrogen would be kept at a minimum. On the other hand, when 

 ammonia or an organic substance capable of yielding ammonia in large 



