Apr. 3, 1916 



Relation of Carbon Bisulphid to Plant Growth 



less. From the data it appears that rcinoculation prevents large accu- 

 mulations of ammonia. This is no doubt due to the oxidation of ammo- 

 nia by the nitrifying bacteria. The figures of the last column (nitrate 

 accumulation) support this statement. A stimulation of ammonification 

 is still noticeable at the end of 3 months. 



The nitrate-forming bacteria apparently do not recover so rapidly 

 from carbon bisulphid treatment as the ammonia-producing organisms; 

 consequently, there is no increase in nitrates until the end of 3 

 months. An exception to this is noted in the reinoculated soil. Here 

 the activity of the nitrifying bacteria is evident 30 days after inoculation. 



In order to ascertain, as nearly as possible, the effect of carbon bisul- 

 phid on the soluble nitrogen of the soil, the figures of Table II, ammo- 

 nia and nitrate nitrogen, -were combined in Table III. 



Table III. — Effect of carbon bisulphid on soluble nitrogen 



Time. 



Ammonia and nitrate nitrogen per loo gm. of dry soil. 



Control. 



Days, 



At beginning 



30 



45 



60 



75 



90 



Mgm, 

 4. 26 

 5-03 



5-13 

 6-59 

 5-05 

 6.94 



2 per cent 



carbon 

 bistilphid. 



Mgm. 

 4. 26 



8.47 

 II. 10 

 8.24 

 8.00 

 9. 06 



2 per cent 



carbon 



bisulphid 



evai>orated. 



Mgm. 

 4. 26 



7-41 



10. 20 



7.82 



7-38 



3 per cent 



carbon 

 bisulphid 

 evaporated 

 + S per cent 

 of soil from 

 control. 



\Igm. 

 4. 26 

 10. 26 

 10. 56 

 6.87 

 7. 10 

 8.90 



From the data in this table it is very evident that carbon bisulphid 

 causes a large increase in ammonia and nitrate nitrogen. There seems 

 to be very little difference between the effect of the various treatments of 

 carbon bisulphid on the formation of ammonia and nitrate nitrogen. 

 When compared with the control soil, it will be seen that 45 days after 

 treatment the carbon-bisulphid soils contain more than twice as much 

 soluble nitrogen. The higher ammonia and nitrate content is very 

 marked 90 days after treatment. A repetition of this experiment gave 

 similar results. 



A review of the data in Tables II and III shows very clearly that carbon 

 bisulphid in Miami soil increases the total soluble nitrogen — namely, 

 ammonia and nitrates. One interesting fact that appears from a com- 

 parison of the ammonia and nitrate content is that these two substances 

 are to a certain degree inversely proportional. 



