EFFECT OF CARBON DISULPHID AND TOLUOL UPON 

 NITROGEN-FIXING AND NITRIFYING ORGANISMS 



By P. L. GainEy 

 Soil Bacteriologist, Kansas State Agricultural Experiment Station 



INTRODUCTION 



In previous publications ^ the writer has presented experimental data 

 showing the effect which carbon disulphid and toluol have upon the 

 total number of bacteria (bacteria that would develop upon agar plates) 

 and upon the accumulation of nitrate nitrogen in soils. It is the pur- 

 pose of this paper to give data showing the effect of similar treatment of 

 soils upon the nitrogen-fixing organisms, together with additiomal data 

 upon nitrification. 



The appearance during the past few years of many excellent reviews 

 of the literature relative to the treatment of soils with volatile anti- 

 septics renders a discussion of previous work unnecessary. The reader is 

 referred especially to the review given by Kopeloff and Coleman. ^ It 

 is sufiicient to say that the results heretofore reported have been very 

 irregular and inconclusive. It is believed that the data reported in this 

 paper will offer, in part at least, an explanation for some of these irreg- 



EXPERIMENTAL METHODS 



In general, the methods used have been similar to those previously 

 employed by the writer. Soils known to possess good nitrogen-fixing 

 and nitrifying powers have been used. Given quantities of soil by weight 

 were treated with varying quantities of carbon disulphid and with toluol. 

 The reagent was then thoroughly mixed in, and the soil immediately 

 placed in an air-tight container and left for three days. At the end of 

 this period those samples from which the reagent was not to be evap- 

 orated were made up to the required degree of saturation with sterile 

 water, the rubber stoppers replaced with cotton, and incubated at room 

 temperature. If the antiseptic was to be evaporated, either the con- 

 tainers were left open or the soil was emptied into sterile petri dishes and 

 left until the soil was air-dry and no odor of the chemical remained. Water 

 was then added and the samples incubated at room temperature. At 

 various stages during treatment or during incubation the nitrogen-fixing 

 ability was tested, and the nitrates present in the soil were determined. 



1 GaiNEY, p. h. THE EFFECT OF TOLUOI, AND CS2 UPON THE MICROFLORA AND FAUNA OF THE SOU,. In 

 Mo. Bot. Gard. 23d Ann. Rpt., p. 147-169. 1912. Literature, p. 168-169. 



EFFECT OF CS2 AND TOLUOL UPON NITRIFICATION, hi Centbl. Bakt. [etc.]. Abt. 2, Bd. 39, No. 



13-25. P- 584-395. 2 fig. 1914- 



* Kopeloff, Nicholas, and Coleman, D. A. a review of investigations in son, protozoa and son, 

 STERILIZATION, /re Soil. Sci., 3, no. 3, p. 197-269. Literature cited, p. 248-269. 



Journal of Agricultural Research, Vol. XV, No. 11 



Washington, D. C. Dec. 16, 1918 



QU Key No. Kans. -17 



(601) 



