292 



SOIL CONDITIONS AND PLANT GRO WTH 



amoebae in Fig. 29. These variations are not accidental and 

 their cause is being investigated. 



The rapid daily fluctuations in numbers apparently bear 

 no relationship to external conditions, such as moisture and 

 temperature. In order to obtain further information daily 

 counts are being made at Rothamsted of the protozoa and 

 bacteria in a field soil for a period of 365 consecutive days. 



Numbers of B&depia & Protozoa, 



J800 

 3600 

 3400 



3200 

 JOOO 



CX) aeoo 



Q 2600 

 CJ S400 



O 



O a200 



^5 ao 

 ^ i80o- 



Q^ I6OO- 



^H ^oo- 

 ^ aoo- 



<c 



IOOO- 

 8OO- 

 00- 



4OO 



aoo 



FIG. 29. Daily counts of active amoeba and of bacteria in Broadbalk Plot 2 

 (dunged) (Cutler and Crump, jy). The active amoebae are given in 

 thousands, and the bacteria in millions, per grm. of soil. 



These observations when completed will also give im- 

 portant information as to the relationship between numbers 

 of bacteria and protozoa. The result of fourteen consecutive 

 daily counts made in February, 1920, is shown in Fig. 29; 

 these show that the numbers of active amoebae and of bac- 



