Apr. 3. 1916 Relation of Carbon Bisulphid to Plant Growth 



17 



The average dry weight of oats in soil treated with carbon bisulphid 

 was slightly greater than that of the control. This difference was most 

 noticeable in the case of reinoculated soil. It appears that the reinocula- 

 tion benefits the action of carbon bisulphid on the growth of oats. The 

 second crop of corn gave the opposite results. The com in untreated 

 soil gave the highest yield. 



EFFECT OF CARBON BISULPHID ON THE ACCUMULATION OF SULPHATES IN 



SOIL 



Very soon after the jars were planted it was observed that the surface of 

 carbon-bisulphid soil was partly covered with needle-like crystals. Quali- 

 tative tests showed that these were made up largely of sulphates, possibly 

 magnesium sulphate. The occurrence of salts was noted in several of 

 the soils treated with carbon bisulphid. Possibly a part of the carbon 

 bisulphid was oxidized to sulphates. It has been reported that a small 

 portion of the carbon bisulphid may be converted into sulphates (4, p. 

 247-251; 10, p. 151-152). 



Samples of the treated and untreated soils were analyzed for sulphates.^ 

 The results are shown in Table XVII. 



Table XVII. — Effect of carbon bisulphid on the accumulation of sulphates in the soil 



Time. 



Treatment. 



Sulphur as 

 sulphates. 



Months. 



3- 



4- 

 5- 

 6. 



Untreated 



2 per cent of carbon bisulphid 



Untreated 



2 per cent of carbon bisulphid 



Untreated 



2 per cent of carbon bisulphid 



Per cent. 



0.023 

 .038 

 .018 



•039 

 . 019 

 . 060 



It is apparent from the data in this table that the addition of carbon 

 bisulphid tends to increase the sulphate content of the soil. 



CONCLUSIONS 



The addition of carbon bisulphid to soil exerts a decided effect on the 

 fauna and flora of the soil. This is characterized by a temporary reduc- 

 tion in the number of micro-organisms. Later, an enormous multiplica- 

 tion of bacteria takes place and an almost parallel increase in production 

 of by-products or soluble nitrogen is noted. The ammonia content seems 

 to follow the curve of bacterial growth and later gives way to larger 

 amounts of nitrate. From the evidence it seems that carbon bisulphid 

 in soil produces an increase in soluble compounds of nitrogen and sulphur. 



• The author is indebted to Prof. W. E. Tottingham, of the Department of Agricultural Chemistry, for 

 the analyses. 



27469°— 16 2 



