Aug. 13. 1917 Effect of Paraffin on A mmonia and Nitrates in Soil 363 



quantities was added, available nitrogen no longer became the limiting 

 factor in fungus growth. Under such conditions the existence of am- 

 monia or an accumulation of nitrate nitrogen to a Hmited extent became 

 possible. 



The extensive use of paraffin in the "paraffin wire-basket method" of 

 studying soil fertility and in similar studies involving the same prin- 

 ciples has been previously mentioned. It might be well to call attention 

 to the extensive comparisons of the manurial requirements as ascer- 

 tained by this method and in actual field tests conducted by the Rhode 

 Island Station (3, 4, 8). This was probably the most comprehensive 

 test of the reliability of the method ever carried out. As a summary of 

 the results, Hartwell and Pember (4, p. 31) have the following to say: 



The frequent failure of the method to secure at different times similar indications 

 regarding the deficiencies of a given soil, even when carried out in the same manner, 

 is the most discoioraging featiu-e concerning the usefulness of the method. The many- 

 instances of disagreement between the results of the basket method and those secured 

 in actual field practice render unreliable the indications which the method in its 

 present form affords regarding the maniuial requirements, at least of certain soils. 



Hartwell and his associates offer no explanation of the anomalous 

 results secured by this method, and, so far as we are aware, no one has 

 explained why so many incorrect indications of manurial requirements 

 were recorded. Wheeler, Brown, and Hogenson (8) do mention in one 

 instance the possibility of denitrification where nitrate nitrogen was 

 added in presence of manure, but attribute this possibility to the manure 

 rather than to the method. 



The results in the present paper undoubtedly offer a satisfactory 

 explanation for the failure of the method we were using in the study of 

 aeration in soils. In these results we also have a probable explanation of 

 the failure of the "paraffin wire-basket method" in the hands of the Rhode 

 Island investigators and in other instances where such failures may have 

 been recorded. No doubt where such a stimulation of saprophytic develop- 

 ment is brought about, not only will nitrogen but also other food ele- 

 ments required in growth be consumed. These facts must all be taken 

 into consideration when paraffin is used in physiological or cultural 

 experiments involving a mixed culture possibly containing organisms 

 capable of utilizing paraffin in their metabolism. The value and sig- 

 nificance of all results heretofore reported as secured under such condi- 

 tions must also be discounted. 



LITERATURE CITED 

 (i) Gardner, F. D. 



1905. THE WIRE-BASKET METHOD FOR DETERMINING THE MANUIUAL REQUIRE- 

 MENTS OF SOILS. U. S. Dept. Agr. Bur. Soils Circ. 18, 6 p., 2 fig. 

 (2) GiLTNER, Ward. 



1913. REPORT OF THE BACTERIOLOGIST. In Mich. Agr. Exp. Sta. 26th Ann. 

 Rpt., 1912/13, p. 149-166. 



