ACTIVITY OF SOIL PROTOZOA 1 
By George P. Koch, 
Research Fellow , the New Jersey State College for the Benefit of 
Agriculture and Mechanic Arts 
INTRODUCTION 
The belief that soil protozoa are destructive to bacteria and, hence, 
are influencing factors in soil fertility is encouraging the more extended 
study of these organisms. It was shown elsewhere (5) 2 that the soil 
contains many cysts of protozoa which become active under favorable 
conditions. To serve as limiting factors in the soil, protozoa must be 
present in the active condition, for it is only as such that they can destroy 
bacteria and other micro-organisms; thus, the question at once presents 
itself, Are the protozoa active in the soil? 
In 1909 Wolff (13) recorded investigations with soil protozoa under¬ 
taken for the purpose of ascertaining whether these organisms lead an 
active life in the soil and of discovering the factors which influence their 
activity. As to the presence of protozoa in the soil, Goodey (2), in 1911, 
concluded that they were not active in normal soils. A few years later, 
however, he (4) found that ciliated protozoa are in the encysted condi¬ 
tion and concluded that the amebae and flagellates were the limiting 
factors in the soil. Martin and Lewin (7) upon examining cucumber- 
sick soils found several different kinds of protozoa. The amebae were 
probably the dominant type, and the flagellates were comparatively few. 
In 1911 Russell and Golding (9) noted that species of Vorticella, Putrina, 
Euglena, and other types present in ordinary soils were also found in 
sewage-sick soils. These organisms were more active in the sewage-sick 
soil than in ordinary field soil. In 1913 Russell and Petherbridge (11), 
in studying “ sickness ” in cucumber soil, found it to be full of organisms 
like myxomycetes, active amebae, eelworms, and other lower animal forms. 
Sherman (12, p. 630), who studied the presence of protozoa in several 
types of soil, summarizes his observations as follows: 
Certain forms of the soil protozoa are active under normal, and even sub-normal, 
conditions of moisture. The active protozoan inhabitants of most soils are probably 
restricted to flagellates. Colpoda cucullus is probably active whenever the moisture 
content is much above normal but does not appear to be so ordinarily. 
1 Contribution from the laboratories of Protozoology, Soil Bacteriology, and Soil Chemistry of the New 
Jersey Agricultural College and Experiment Station. 
Reference is made by number to “literature cited,” p. 488. 
Journal of Agricultural Research, 
Dept, of Agriculture, Washington, D. C. 
bd 
(477) 
Vol. V, No. 11 
Dec. 13, 19x5 
N.J .-3 
