EFFECT ON PROPERTIES OF SOIL 129 



the treatment of soils with carbon bisulphid acts unfavorably upon 

 the water content of the soil. 



Other characteristic effects of treatment with volatile antiseptics 

 reported by various investigators are : 



1. An initial decrease in the number of bacteria followed by a 

 long-continued increase. A careful piece of experimentation illus- 

 trating this is that of Fred who used loam soil (mixed with sand) 

 and found that 2 per cent, carbon bisulphid has little effect upon 

 the moisture content of the soil. With varying percentages of ether 

 (together with 2 per cent, of sugar) in the soil, he finds an initial 

 depression in bacterial numbers followed by a considerable increase 

 in eight hours, 4 per cent, giving the maximum count. 



2. A disturbance of the equilibrium of the bacteria, by which 

 certain types multiply more rapidly than others. Hiltner and 

 Stormer found that under normal conditions there is a certain 

 equilibrium established among the various groups of soil bacteria, 

 and that the organisms capable of growing on meat extract gelatin 

 are composed of Streptothrir species 20 per cent., gelatin-liquefying 

 species 75 per cent., and the non-liquefying species 5 per cent. 



When carbon bisulphid is applied to a soil, its bacterial inhabitants 

 are injured, though not completely destroyed, the injury varying 

 with the changing conditions of temperature, moisture, and amount 

 of carbon bisulphid applied, as well as with the duration of its action. 

 Not all of the bacterial species are depressed in their development 

 to an equal extent, the injury being most pronounced in the strepto- 

 thrix species and least pronounced in the gelatin-liquefying species. 

 The depressing action of carbon bisulphid disappears after a shorter 

 or longer interval and is followed by a rapid multiplication of the 

 microorganisms in the soil. The equilibrium having been destroyed, 

 however, the new development follows along different channels, 

 and there occurs not only an enormous increase in the total number 

 of soil bacteria, but also an abnormal predominance of certain 

 species. The new conditions thus established for a time favor a 

 more ready utilization of the stores of soil nitrogen, and likewise the 

 fixation of atmospheric nitrogen by certain bacterial species. These 

 conclusions are borne out by the work of Lipman and Brown who 

 examined abnormal soil after applying carbon bisulphid in various 

 quantities alone, and in combination with muriate of potash and 

 acid phosphate. They then determined the ammonifying, nitrifying, 

 denitrifying, and nitrogen-fixing powers of the soil. They concluded 

 that in normal soil flora the different groups occur in fairly definite 

 relations which are evidently disturbed by the addition of carbon 

 bisulphid, which, destroying the bacterial equilibrium prepares the 

 way for an entirely new bacterial development whereby certain 

 species become far more prominent than previously. This applies 

 especially to the nitrifying and nitrogen-fixing bacteria. 

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