EFFECT OF STEAM STERILIZATION ON THE WATER-SOLUBLE 



MATTER IN SOILS 



The use of carbon bisultid and later of steam for the purpose of destroy- 

 ing injurious organisms in soils has led to a study, by a number of in- 

 vestigators, of the effects of these operations on the chemical and bac- 

 teriological properties of soils. It has, undoubtedly, been shown that 

 whether sterilization be complete, as may be accomplished by heat- 

 ing with steam under pressure, or whether it be only partial, as is the 

 case when steaming is done at lower temperatures and for shorter periods 

 or when volatile antiseptics are used, the effect on the soil is to increase 

 the water-soluble matter and greatly to modify the normal relations 

 of the bacterial flora. It therefore offers a good opportunity to study 

 changes which may occur in soils. Much emphasis has been laid on the 

 importance of bacteria in the processes by which the amount of water- 

 soluble matter is increased, but there can be no doubt that, with steam 

 at least, important changes are produced that are purely chemical. It 

 would seem to be desirable to study carefully the chemical changes im- 

 mediately produced, and which precede and make possible the later 

 bacterial activity. Admittedly the immediate eflfects produced by steam 

 at high pressure are not bacteriological. We have therefore used that 

 treatment in our preliminary w^ork. 



This paper treats only of the chemical changes in the soils used. On 

 some of the soils plants were grown to indicate the effect of the changes 

 on plant growth. The authors are indebted to Dr. John H. Squires for 

 most of the data on plant growth, which work he performed in connec- 

 tion with his study of certain properties of these soils, a monograph on 

 which he presented to the faculty of Cornell University as a thesis for 

 the degree of Doctor of Philosophy. 



Reports by the various investigators in this field show differences in 

 results which indicate that soils of various kinds may be quite differently 

 affected by sterilization. The following is a brief review of the published 

 experiments on the effect of heating soils with steam. 



REVIEW OF EXPERIMEXTS ELSEWHERE 



Richter* found that heating a garden soil in an oven at ioo° C on 

 three successive days increased its absorptive power for water and the 

 amount of nitrogen soluble in water and dilute hydrochloric acid, while 

 the water-.soluble organic matter was increased about threefold. 



Pfeiffer and Franke steamed soil at one atmosphere pressure for three 



'Landw. Versuchs. Stat. 47 (1896) p. 269 



*Landw. Versuchs. Stat. 46 (1896) p. 117 '. 



247 



