AND COLLEGE, PUSA, FOR 1914-15. 19 



In the case of swamp paddy soil gases, the amount of 

 dissolved oxygen and nitrogen has an important bearing. 

 Messrs. Harrison and Subramania Aiyer have given reasons' 

 for assuming that the dissolved oxygen is of importance 

 both to the surface film and to the roots of the plant below. 

 Calculations regarding the sources of the nitrogen in the 

 gases have shown that probably about one-third of it is 

 derived from the dissolved nitrogen of the irrigation water. 



Regarding the examination of soil gases generally it is 

 of importance not merely to ascertain the proportions of 

 oxygen and carbon dioxide present. Although our know- 

 ledge of the biology of the soil is so imperfect, the general 

 conclusion that oxygen is commonly used up in the produc- 

 tion of carbon dioxide is no doubt justified, but the ordi- 

 nary gas analysis might not show whether oxygen was 

 being utilized in other ways. Again percentages of oxygen 

 and nitrogen do not themselves show whether there has 

 been an absorption of the one or an evolution of the other. 

 For example supposing nitrogen gas were being liberated 

 the effect would be an increased per cent. N, a decreased per 

 cent. 0; but these figures would not show whether oxygen 

 was being absorbed by the soil or nitrogen liberated. An 

 important case of this nature is the origin of the nitrogen 

 in paddy land gases. Messrs. Harrison and Subramania 

 Aiyer after discussing the matter 2 by means of indirect 

 evidence, concluded that a part of the nitrogen in these 

 gases was derived from the organic matters of the soil and 

 manure, but a means of directly testing the question was 

 clearly of importance. Such a question could be solved by 

 the estimation of a gaseous element which takes no part in 

 biological processes. The gases present in the soil are 

 derived from (i) the outside atmosphere and (ii) the pro- 

 ducts of biochemical change. Hence if the nitrogen in the 

 soil were derived solely from the atmosphere, its ratio to 

 the rarer elements, argon, helium, etc., in the soil gases 

 should be the same as in the atmosphere, whilst if nitrogen 



1 Mem. Deft. Agric. Ind., vol. Ill, no. 3, p. 81. 

 3 Loc. cit., p. 82. 



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