E. J. Russell and A. Appleyard 

 Bry conditions 



33 



The low amount of CO., relative to the oxygen used up has already 

 been discussed (p. 19). 



Minor fi net uaf ions in composition of the soil air. 



We now turn to a consideration of the minor fluctuations in 

 composition of the soil air. These differ fundamentally from the major 

 fluctuation hitherto dealt with in as much as they are probably not 

 associated with the production of COg in the soil but only with variations 

 in the agencies causing loss. They are brought about by two causes : 



(1) Variations in the soil itself: shown in Table XI (p. 41) and 

 discussed on p. 4. 



(2) Variations in meteorological and cultivation conditions. 



The only satisfactory way of dealing with the effect of meteorological 

 conditions on the soil atmosphere is by statistical methods, but although 

 we have many records we do not feel that they are sufficiently numerous 

 for the purpose. We have, however, tested certain broad and obvious 

 possibihties, the data for which are found in Table VI (p. 46). 



(a) Rapid change of temperature. It has happened on a warm day 

 preceded by a frosty night, i.e. where the temperature altered quickly 

 and considerably, that the soil air approximated closely in composition 

 to atmospheric air indicating that it had been largely replaced by 

 atmospheric air. Instances occur on January 13th and February 26th, 

 191.3. 



[b) High rainfall. In view of the quantity of bicarbonates in 

 drainage water it is important to ascertain whether high rainfall 

 appreciably diminishes the amount of COg in the soil air. The observa- 

 tions do not yield any very definite results : in some cases the immediate 

 effect is to reduce the COg but not always, while usually the subsequent 



Joiun. of Agric. Sei. vii 3 



