JOim OF AGRiaJLTlAL MARCH 



DEPARTMENT OF AGRICULTURE 

 Voiv. VI Washington, D. C, April 3, 1916 No. i 



RELATION OF CARBON BISULPHID TO SOIL ORGAN- 

 ISMS AND PLANT GROWTH^ . 



By E. B. Fred, 



Agricultural Bacteriologist, Agricultural Experiment Station 



of the University of Wisconsin 



INTRODUCTION 



In a previous publication concerning the action of carbon bisulphid 

 (CS2) on bacteria and plants data were presented to show the beneficial 

 effect of this substance on the soil flora (i)." The increased plant growth 

 following the addition of carbon bisulphid in many cases is enormous. 

 For example, a small application often causes an increase in yield from 

 100 to 200 per cent. It is impossible to account for this remarkable gain 

 on the assumption that the only action of the carbon bisulphid is that of 

 added plant food. It was found, as has been noted by many investi- 

 gators (5, 6, II, 12), that this volatile antiseptic exerts a very decided 

 effect on the micro-organisms of the soil. As measured by plate counts, 

 there is at first usually a great decrease in numbers, followed by a period 

 of excessive increase, the total numbers far exceeding those that ordinarily 

 exist. In certain cases carbon bisulphid has not only failed to cause an 

 increase in plant growth, but has, on the contrary, caused a decrease. 



Search has been made by many investigators for a satisfactory ex- 

 planation of this peculiar action of carbon bisulphid. Many theories 

 have been advanced. Concerning these theories so much has been 

 written that a detailed discussion of the literature seems unnecessary. 

 Indeed, it would be impossible within the limited scope of this paper to 

 present a summary of the various explanations. One point is very 

 prominent in nearly all of the publications : The action of carbon 

 bisulphid is varied. Because of the interest attached to this problem, 

 it was arranged to study some of the factors that might influence 

 the action of carbon bisulphid. The experiments described in this paper 

 are discussed under three main heads : First, the effect of varying 

 amounts of carbon bisulphid; second, the effect of carbon bisulphid on 

 various plants; and third, the effect of carbon bisulphid in various soils. 

 In all of this work fresh field soil and commercial carbon bisulphid 

 were used. vSome of the experiments represent a combined study of the 

 effect on both the lower and higher forms of plant life. 



1 Published with permission of the Director of the Wisconsin Agricultural Experiment Station. 

 * Reference is made by number to "I,iterature cited," p. i8-ig. 



Journal of Agricultural Research, Vol. VI, No. i 



Dept. of Agriculture, Washington, D. C. Apr. 3, 1916 



cu (l) * Wis.— 5 



