248 Bulletin 275. 



hours. The soil so treated produced a crop of greater dry weight and 

 higher nitrogen content than the unheated, even when the sterile soil 

 was inoculated by portions of the fresh. 



Deherain and DeMoussy^ prevented nitrification in two soils by heat- 

 ing them at 120° C in an autoclav for one hour. The sterilized soil, how- 

 ever, when inoculated with a portion of the unsterilized produced a 

 much larger quantity of nitrate nitrogen than did the unsterihzed soil. 

 It was also observed that sterilization had the effect of increasing the am- 

 monia nitrogen content, while a considerable quantity of carbon dioxid 

 was also produced by the treatment. 



Stone and Smith^ working with soil partially sterilized in an effort to 

 destroy insects and fungous diseases, found that a sterilized loam soil 

 with a fair amount of organic matter produced good crops while a ster- 

 ilized subsoil produced poor ones. There appeared to be some relation 

 between the content of organic matter and the effect on the crop. 



Kruger and Schneidewind^ in experimenting to determine the cause 

 of dentrification, incidentally noticed that steam sterilization caused 

 a large increase in crop growth and in the nitrogen content of the crop, 

 even when nitrate nitrogen was added to the soils. 



Schulze* found that sterilization of the soils with which he worked 

 had a more or less unfavorable effect on plants, which he atrributed to 

 chemico-physical changes. The effect was greatest on meadow soil, 

 less on field soil and least on garden soil. Oats were found to be less 

 sensitive to this influence than mustard. Even though sterilization 

 caused a smaller crop the nitrogen content was greater than in the crop 

 from the unsterilized soil. Later he published an article* stating that 

 in his experiments sterilization produced injurious effects on the crop 

 in the early stages of growth, but as the plants grew older they became 

 more vigorous on the sterilized soils. Sterilization appeared to produce 

 injurious decomposition products and to increase the amount of avail- 

 able plant food. The effect on the crop depended on the predominance 

 of one of these influences and the sensitiveness of the individual crop. 



Gerlach and VogeP grew corn in sterile soil fertilised both with sodium 

 nitrate and ammonium sulfate. Ammonium sulfate produced almost 

 as great an increase as did sodium nitrate, when plants were grown 

 under sterile conditions. 



*Ann. Agron. 22 (1S96) p. 305 



'Mass. Hatch Sta. Reports 1902, p. 74; 1903, p. 40; 1906, p. 125 



'Landw. Jahr. 1899 (5) p. 228 



■•Abstract Centrb. f. Bakt. 2 abt. 11 (1903) p. 716 



*Landw. Versuchs. Stat. 65 (1906) p. 137 



•Cent. f. Bakt. II. 14 (1905) p. 124 



