Sttu/ien on JSoil rrotozoa 



Table 18. 



Number of 

 Experiment 



Mgs. nitrogen as aiuiiiuuia in solution containing :- 



Bacteria + Protozoa 



As to the appearance of the cultures with and without protozoa 

 the latter have generally been somewhat brown in colour, the former 

 greenish. Further the two sets of solutions smell quite differently. 

 In the protozoa cultures the \nle-smelling decomposition products 

 usually associated with ammonification appear to be absent. 



It had been intended to cany this section of the work much further 

 but circumstances unfortunately do not permit. The results, so far as 

 obtained, do not justif}' any very definite conclusions. The organisms 

 dealt with are, with one exception, the flagellates, and it seems probable 

 that these may have a depressing influence on ammonification. The 

 whole question, however, requires to be thoroughly investigated. 



VI. The Inoculation of Protozoa into partially 



STERILISED SoiLS. 



In the second paper of Russell and Hutchinson' on the effect of 

 partial sterilisation of soils, it is stated that the authors have failed to 

 observe a depression in the numbers of bacteria in partially sterilised 

 soils as a result of inoculation with mass cultures of protozoa. This 

 is attributed to the great multiplication of bacteria which takes place 

 on the introduction of the considerable (|uantity of nutrient material 

 contained in the culture. Greig Smith^ al.so failed to obtain a reduction 

 in the numbers of bacteria, nftoi- inoculalion of ]),irtially sterilised soil 

 with protozoa cultures. 



Two experiments bearing on this point have been carried out here. 

 For the first experiment 500 grams of air-dry soil was passed through 

 a ■2 mm. sieve. 2-5 c.c. formahn in 20 c.c. water was rubbed up with 



' Joiini. of Agric. Sc. v. 2, p. 152. 



* Proc. Linn. Soc.N.S. HWe.«, Abstracts, 1912, pp. 2-3: Rol.CenlraWl.f. Bnkl. Abt. ii. 

 Bil 39, p. I.'')2. 



