ACTIVITY OF SOIL PROTOZOA* 



By George P. Koch, 



Research Fellow, the New Jersey State College for tJie 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)^ 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 191 1, 

 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 amebse were 

 probably the dominant type, and the flagellates were comparatively few. 

 In 191 1 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 191 3 Russell and Petherb ridge (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, Vol. V, No. 11 



Dept. of Agriculture, Washington, D. C. Dec. 13, 1915 



bd N. J— 3 



(477) 



