AND COLLEGE, PUSA, FOR 1914-15. 81 



observation. It was found in the laboratory that super- 

 phosphate had a neutralizing action upon the toxicity to 

 bacteria of extracts of certain soils and this was traced to 

 the free acid; this result, however, was not sufficiently 

 conclusive to allow of its use as a convincing explanation 

 of the favourable action of superphosphate upon water- 

 logged soils, although this theory is supported by Meggitt's 

 work in Assam, but will require further experimental 

 investigation. 



Ammonification proceeded at the normal rate in soil 

 under semi-anaerobic conditions and was apparently not 

 interfered with by the bacterio-toxins produced although 

 the activity of such ammonifiers as B. mycoides is actually 

 lowered by the presence of Bacillus X. ; this latter organism 

 does not appear to be universally present in soils; no con- 

 centration of ammonia above that in the aerated control 

 was found nor was this gas given off by the anaerobic soil. 

 The action of carbon dioxide in excess was eliminated by 

 absorption with potash, as well as by the use of the soil 

 extract as mentioned above. 



A special experiment was made to test the action of 

 the carbon dioxide formed in soil by bacterial action upon 

 nitrification in that soil; under partially anaerobic condi- 

 tions absorption of the carbon dioxide produced no effect 

 upon nitrification in soil, either of oilcake or of ammonium 

 sulphate; in this experiment, the observation was repeated 

 that complete nitrification of ammonium sulphate took 

 place under semi-anaerobic conditions in which no nitrifica- 

 tion of oilcake occurred. 



It appears therefore that in soils in which aeration is 

 incomplete, as a consequence either of want of proper 

 cultivation or of drainage, the decomposition of organic 

 matter by such bacteria as thrive under these conditions 

 will result in the production of toxins inhibitory of nitri- 

 fication. It has also been shown that these toxins are 

 destroyed by exposure to air and can be removed in water 

 solution, so that the ordinary operations of tillage and 

 drainage can prevent their accumulation. 



G 



