36 



The Afliioxp/iirr of flu Soil 



brings out several important features \vhi(-li \vc must now proeeed to 

 discuss. 



Fig. 11 shows the rainfall, bacterial numliers. carbon dio.xitlc and 

 nitrate for the Broadbalk dunged plot, which is perhaps the most 

 convenient for our purpose by reason of the high values it yields. 

 Beginning in July, ]913, the bacterial numbers follow the rainfall very 

 closelv till OctoliiT ami less closely till .lanuaiy, the diminishing raiiifaii 



Table IX. Prnentafje composilion of soil air before and ufle. 

 cultivation ojierations. 



•er 



of Julv and August being accompanied by a fall in bacterial numbers, 

 the September rain by a rapid rise, and so on. The COj curves also 

 follow in the same way but later in point of time and they are somewhat 

 smoothed out: thus they do not show the kink in October. The nitrate 

 curves again show the same rise but still later; in (-omparing them with 

 the others, however, it must be remembered that conditions of drought 

 which favour a decrease of bacteria through death and of CO.^ through 

 ditTusion have no oft'cct in rofhu-ing the amounts of nitrate: thus during 



