Apr. 3, 1916 



Relation of Carbon Bisulphid to Plant Growth 



this means it was hoped to prevent a rapid volatilization of the anti- 

 septic. The jars were not planted until three months after treatment. 



At the beginning and at intervals of one, two, and three months 

 bacterial activity was measured. Naturally, under the conditions of this 

 experiment, carbon bisulphid proved very drastic. A great reduction in 

 the number of bacteria, without any increase until the second month, 

 was noted. The relation of carbon bisulphid to the number of bacteria 

 was about the same in all three series. In the more compact type, 

 Miami silt-loam soil, the carbon bisulphid proved most injurious to num- 

 bers, and consequently the period of increase was much later. Of the 

 three soils, the treated sand showed the greatest proportional gain in 

 number of bacteria. 



Because of the severe nature of the carbon-bisulphid treatment, it was 

 thought that probably the protozoa would be destroyed or the number 

 greatly diminished. This was not the case, however, as protozoa were 

 found in great numbers in both the treated and untreated soil. 



Three months after treatment the jars were divided into two series and 

 planted. The weights of the first and second crops are given in Tables 

 VIII and IX. 



Table Ylll.— Effect of carbon bisulphid on the growth of buckwheat and mustard in 



different types of soil 



The figures of the buckwheat crop show the same general increase as 

 noted in a previous experiment. Although not great, the gain in the 

 treated series is consistent in all three soils. 



The residual crop of mustard responded to a very marked degree to 

 the carbon bisulphid treatment. In Miami silt loam the yield from the 

 treated soil exceeded that of the control by more than loo per cent. The 

 gain in weight of oats in the treated soils was not so great, while the 

 second-crop corn showed a loss (Table IX). 



