JOm£ OF AGRianiMiAL ISEMCH 



Vol. XIII Washington, D. C, April 22, 1 91 8 No. 4 



RELATION BETWEEN BIOLOGICAL ACTIVITIES IN THE 

 PRESENCE OF VARIOUS SALTS AND THE CONCEN- 

 TRATION OF THE SOIL SOLUTION IN DIFFERENT 

 CLASSES OF SOIL ' 



By C. E. Millar - 



• ' ^K A K y 



Assistant Professor of Soils, Michigan Agricultural College Experiment Station '^6 IV V01>if 



INTRODUCTION ®*^ANICaL 



Experiments dealing with the concentration of the soil solution in soils 

 of different classes when treated with various salts have been in progress 

 in this laboratory for some time, and it has now become very desirable 

 to know the relation between the biological activities and the composition 

 and concentration of the soil solution under these conditions. 



Several workers have shown that certain salts occurring naturally in 

 many soils and often added as fertilizers and amendments have pro- 

 nounced effects on the bacterial flora present. The causes of these 

 effects have not been entirely determined, it being assumed that both 

 toxicity and osmotic pressure are operative. 



HISTORICAL REVIEW 



No attempt will be made to give a complete resume of the literature on 

 toxicity, but the writer wishes to call attention to a few points brought 

 out by various investigators. 



A review of the available literature on the toxicity of salts for higher and 

 lower plant life shows considerable disagreement in the results obtained 

 by different investigators. It is suggested by Greaves ^ that in many 

 cases this may be explained by the unknown variation in the actual 

 amounts of salts added, and he proposes to remedy the deficiency by 

 analyzing the solutions used to supply the salts and correcting for the 

 variations found. 



Greaves ^ found that calcium nitrate, magnesium nitrate, calcium 

 chlorid, sodium sulphate, and potassium sulphate were toxic to the 



* Publication authorized by Dean R. S. Shaw, Director of the Michigan Agricultural Experiment Station. 



' The writer wishes to express his gratitude to Dr. M. M. McCool, of the Michigan Experiment Station, 

 for many helpful suggestions during the completion of these experiments and preparation of the manu- 

 script. 



^ Greaves, J. E. the iNFtuENCE op salts ok the bacteriai, activities of the soil. In Soil Science, 

 V. 2, no. 5. p. 443-480, 4 fig. 1916. 



Journal of Agricultural Research, Vol. XIII, No. 4 



Washington, D. C. Apr. 22, 1918 



nd Key No. Mich.-8 



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