86 KANSAS UNIVERSITY SCIENCE BULLETIN. 



Greig-Smith 11 claims to have shown that volatile antiseptics 

 are beneficial to such toxic soils. He claims that the former 

 dissolve out and absorb the toxic ingredients and remove them 

 from the sphere of activity, the so-called rhizoplane or root 

 zone. He thus accounts for the beneficial action commonly 

 secured when soil is treated with CS,. Heating of soil as prac- 

 ticed in the partial sterilization of soil is likewise supposed to 

 eliminate the toxic action or rather detrimental action mani- 

 fested by such soils. Russell and Hutchinson 12 attribute the 

 beneficial action of partial sterilization or antiseptification of 

 soil to the destruction of certain forms of life which ordinarily 

 prey upon the bacteria concerned in the conversion of unavail- 

 able plant food to available forms. They regard the protozoa, 

 amoeba and ciliates as competitive factors in the soil. If re- 

 moved, the bacteria have full control and so can continue their 

 multiplication with subsequent elaboration of plant food. 



It is thus apparent from the above discussion that a multi- 

 plicity of hypotheses have been advanced to explain various 

 phenomena manifested by soils which appear to give reduced 

 crop yields. No doubt one can not attribute to any single factor 

 the responsibility for the reduced productivity. Instead it ap- 

 pears far more probable that many factors contribute and co- 

 operate to bring about aforesaid phenomena. In the light of 

 the very complex nature of the soils, this seems the more prob- 

 able and the only reasonable view to take relative to the prob- 

 lem in hand. 



On the basis of the numerous explanations regarding this 

 matter or closely related phenomena advanced by various in- 

 vestigators, it would appear that the soil bacterial flora must 

 be regarded as a most important agent, responsible, at least in 

 part, directly or indirectly, for the reduced crop yields on con- 

 tinuously cropped soils. Their action must undoubtedly center 

 in their ability to decompose the various vegetable debris con- 

 stantly being returned to the soil. 



That the bacterial flora of the soil may be influenced by con- 

 tinuous one-cropping and that the bacteria in turn may in- 

 fluence subsequent crops, either the same or different, by the 

 production of by-products harmful or beneficial to the plants, 

 are matters which have as far as is known been largely ignored 



11. Gentbl. Bakt., 2 Abt., vol. :S(), pp. 154, 156. 



12. Russell and Hutchinson, Journal Agricultural Science, 1011, vol. 3, p. Ill: 1912 

 fol. 5, pp. 27, 86; 1913, vol. 5, p. 152, ' 



