Investigations on protozoa in relation to the factor limiting bacterial activity in soil

Abstract

In the course of my work on soil protozoa particularly in relation to the question of the partial sterilisation of soil, I had occasion to work with some of the old stored soils kept at the Rothamsted Experimental Station, Haependen, at which laboratory the work here recorded was commenced. These soils are remarkable for the length of time they have been stored, 67 years being the longest period, and for the fact that in many cases the original samples put up in large bottles have remained untouched since the day on which they were bottled. Preliminary cultures of some of these soils in hay-infusion were begun in 1912 to ascertain the character of the protozoan fauna, if such still persisted in them. From these cultures it was found that in a mixed sample from Broadbalk, bottled in 1846 and containing about 3 per cent. of water by weight, no protozoa were present, whilst in another mixed sample taken from six bottles of Barnfield soil, put up in 1870 and containing about 10 per cent. of water by weight, amœbæ and flagellates but no ciliates were present.