HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Jackson, N. E. Articles by Picken, J. C. Search for Related Content PubMed Articles by Jackson, N. E. Articles by Picken, J. C., Jr. Agricola Articles by Jackson, N. E. Articles by Picken, J. C.

Gamma Irradiation and the Microbial Population of Soils at Two Water Contents¹

ABSTRACT

Thirty-gram soil samples, in plastic tissue culture dishes (60 x 15 mm), were irradiated with gamma rays (8000 curie Co-60 source) at doses ranging from 0 to 3 million rads. Fungal and bacterial plus actinomycetal counts were made by plating soil suspensions on rose bengal-streptomycin agar and egg albumin agar, respectively. Plates were incubated for 4 to 8 days before counting. The numbers of fungal and bacterial units reflected differences in survival among the microbial populations from soil samples taken at three horizons within field profiles. Microbial counts in the soils at 30% water content (by weight) were generally reduced to zero at lower radiation doses than those in the air-dry soils. One million rads were required to kill all fungi, but 2 to 3 million rads were required to kill all bacteria in a 30-g soil sample. At a given water content, samples with the higher initial microbial populations required greater radiation doses for sterilization than samples with lower populations. For small soil samples, exposure to gamma radiation proved a rapid and efficient method of sterilization.

Key Words: soil sterilization • soil irradiation • water content

¹ Journal Paper no. J–5518 of the Iowa Agr. & Home Econ. Exp. Sta., Ames, Iowa. Project no. 1378. Contribution from the Department of Agronomy. Presented before Div. S-3, Soil Science Society of America, Aug. 22, 1966, at Stillwater, Okla. This work was supported in part by Phillips Petroleum Company, Bartlesville, Okla. and by the US Atomic Energy Commission, Contract no. AT-(11-1)-1269. Report no. COO-1269-12.

^2,3,4 Research Assistants in Soils, Professor of Soils, and Professor of Veterinary Physiology and of Biochemistry, Veterinary Medical Res. Inst., Iowa State University.

Received for publication October 7, 1966. Accepted for publication March 15, 1967.