JOMALOFAGMQUIAIISEARCH 



Vol. XII Washington, D. C, February 25, 1918 No. 8 



INFLUENCE OF CARBONATES OF MAGNESIUM AND 

 CALCIUM ON BACTERIA OF CERTAIN WISCONSIN 

 SOILS ^ 



By H. ly. FuLMER,^ 

 Assistant Agricultural Bacteriologist, Wisconsin Agricultural Experiment Station 



THE PROBLEM 



In the course of a study of the biology of certain acid soils it was 

 tound that magnesium carbonate causes a great increase in the reproduc- 

 tion of soil bacteria. Just what effect this great increase in number of 

 bacteria has on the fertility of the soil is a problem beyond the scope of 

 this paper. However, it is a well-established fact that the majority of 

 the changes of soil constituents are brought about by microorganisms. 

 These substances, which are constantly undergoing changes, are influ- 

 enced by the number and kinds of bacteria. 



The beneficial effect of lime, calcium carbonate, and magnesium car- 

 bonate on the growth of higher plants is generally preceded by an increase 

 in the number of bacteria. Evidence is sufficient to warrant the con- 

 clusion that an increase in the number of soil microorganisms is usually 

 reflected in a more rapid decomposition of organic matter and a greater 

 liberation of the inorganic soil constituents, chiefly potassium and phos- 

 phorous. 



Although many important data have been obtained in relation to the 

 effect of liming on the bacteria in soil, there still remain problems which 

 deserve careful investigation — for example, the amount and kind of lime 

 and calcium and magnesium carbonates that can be applied most eco- 

 nomically and yet give the best results. 



The investigations of this paper were undertaken with the hope of 

 throwing some light jpon the problem of soil bacteria and their response 

 to applications of magnesium carbonate, calcium carbonate, and limestone. 



The effect of these substances on pure cultures of bacteria and on the 

 ordinary soil flora was observed in — 

 (a) Acid Colby silt loam soil; 

 (6) Acid Plainfield sand; 

 (c) Neutral Miami silt loam. 



' This paper is submitted in partial fulfillment of the requirements for the degree of doctor of philosophy 

 in bacteriology in th^ Graduate School of the University of Wisconsin, July, 1917. 



' The writer is indebted to Dr. E. B. Fred, of the Wisconsin Experiment Station, for supervision and 

 suggestions in the experimental work and preparation of the manuscript. 



Journal of Agricultural Research, Vol. XII, ^fo. 8 



Washington, D. C. Feb. as, 191S 



me Key No. Wis.— ir 



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