Aug. 13, 1917 Effect of Paraffin on Ammonia and Nitrates in Soil 357 



milligrams of nitrogen per 100 gm. of soil. "Active nitrogen" repre- 

 sents the total quantity of nitrogen present both as NO3 and NH3. 

 Ammonia was tested qualitatively with Nessler's reagent. Where it is 

 reported as a "trace," only slight color resulted from the test. Where 

 it is reported as "good," a strong yellow color was developed. Where it 

 is reported as "abundant," a heavy brick-red precipitate was formed 

 when the reagent was added to the clear solution. 



RESULTS OF EXPERIMENTATION 



The results presented in Tables I, II, and III are certainly very striking 

 and show conclusively that paraffin can not be employed in investigations 

 such as are mentioned earlier in this paper, unless the microbial flora is 

 absolutely under control as regards the species present in the biological 

 pabulum. 



When nitrogen was not added, regardless of whether calcium car- 

 bonate was added, the presence of paraffin in the three forms here 

 used completely inhibited the accumulation of both ammonia and 

 nitrate nitrogen. Not only did it prevent further accumulations of 

 nitrate nitrogen but actually caused all that was present at the 

 beginning of the experiments to disappear. The effect was main- 

 tained for the longest period here recorded, 13 weeks, and similar 

 results have been observed for even longer periods of incubation. 

 The above relations held true whether the paraffin was intimately 

 mixed into the soil or simply lined the inner wall of the container. 

 In the latter case the quantity of paraffin actually coming in contact 

 with the soil was rather limited. 



When cottonseed meal was added as a source of nitrogen, vigorous 

 ammonia and nitrate formation took place in the presence of paraffin. 

 Owing to the very rapid subsequent disappearance of both ammonia 

 and nitrate nitrogen, their formation is sometimes not apparent, and 

 it is impossible to say whether such formation was equally as rapid 

 as in the absence of paraffin. In no case after the 2 -week analysis 

 does the quantity of ammonia or nitrate nitrogen, where Parowax or 

 paraffin was present, even approach the quantity in the controls. 

 Differences in favor of the controls are evident even at the end of 

 one week, and with both these forms of paraffin the active nitrogen 

 (NOa-fNHg) soon falls to a mere trace. Where paraffin oil was 

 added, the results are somewhat different. During the early stages 

 of incubation the inhibitory effect upon the accumulation of both 

 forms of nitrogen is more marked than v/ith other forms of paraffin. 

 In the case of the oil the effect appears to be quite largely an inhibi- 

 tion of formation rather than a disappearance of ammonia and nitrate 

 nitrogen, for, as incubation progresses, the quantity of active nitro- 

 gen approaches very closely that present in the controls. The de- 

 creased accumulation of both forms of nitrogen in the presence of 

 Parowax and paraffin is more marked where they are mixed into 

 the soil than where only surrounding it. 



