816 EXPERIMENT STATION RECORD. 



development, sturdier and healthier plants, earlier flowering, more prolific 

 fruiting, and better quality of fruit. 



" It is particularly useful for commercial glasshouses where soil pests are a 

 source of trouble, and soil ' sickness ' sets in. 



"At present the most effective method of partial sterilization is to heat the 

 soil to a temperature above 140° F., but not exceeding 212° F. Very satis- 

 factory results have been obtained between ISO and 200° F. ; i cwt. or less 

 fuel is required per ton of soil ; capital and labor charges depend on the speed 

 at which the process is to be worked. Our experiments indicate that effective 

 chemical treatment is also possible, and would, of course, be much simpler, but 

 we have not yet tested a sufficient number of commercial products to discuss 

 the problem from the grower's point of view." 



Bacterial activities in frozen soils, P. E. Brown and R. E. Smith {Ahs. in 

 Science, n. ser., 35 {1912), No. 897, p. 380). — In this paper, which was presented 

 at the Washington meeting of the American Chemical Society in 1011, the 

 authors report investigations made during the winter months of 1910-11, in 

 which it was found " that bacteria which developed on synthetic agar plates, 

 ammonifying, nitrifying, denitrifying, and nitrogen-fixing species whose activities 

 were tested by the beaker method, were alive and multiplied in frozen soils. 



" In explanation of this, the theory is advanced that when soils freeze the 

 hygroscopic water remains uncongealed, because of the surface tension exerted 

 by the soil particles on the film water, its normal concentration in salts, and 

 its increased concentration occurring when the main body of soil water begins 

 to freeze. 



" Temperature exerted more influence than moisture on the bacteria develop- 

 ing on the agar plates." > 



Contributions to our knowledge of soil fertility, II. — The determination 

 of Ehizobia in the soil, R. Greig-Smith {Proc. Linn. Soc. N. S. Wales, 36 

 (1911), pt. 3, pp. Ji92-503). — The author reports upon the method of growing 

 soil organisms by which he is able to demonstrate the number of Azotobacter 

 in soil. In the course of his investigation it became apparent that the most 

 numerous nitrogen-fixing organism present was the Rhizobium, and a report is 

 given on the determination of this organism in various samples of soil by the 

 selective medium method. To a certain extent, there seemed to be a parallel 

 between the fertility of the soil and the number of Rhizobia contained in it. 

 The effect of cultivation is to increase greatly the numbers of these organisms 

 in a given soil. 



Summarizing his results, the author states that the number of nitrogen- 

 fixing Rhizobia in agricultural soils A'aries from 3 to 4 millions per gram, and 

 that the number present affords an indication of the comparative fertility of 

 the soil. 



Certain factors limiting' nitrification, I. G. McBeth and R. C. "Weight (Ahs. 

 in Science, n. ser., 35 {1912), No. 891, p. 392). — The following summary of a 

 paper presented at the Washington meeting of the American Chemical Society 

 in 1911 is given : 



" Two per cent of glucose and 2 per cent of starch disappeared from soil in 

 less than 7 days. Cellulose disappeared more slowly. The addition of glucose 

 and starch caused a rapid disappearance of nitrate from eastern and western 

 soils ; with cellulose the reduction of nitrate was less rapid. 



" Two per cent of fresh horse manure caused only a partial disappearance of 

 soil nitrate. After 7 days in eastern soil and 21 days in western soil nitrifica- 

 tion became active, causing an increase in nitrate. 



" Nitrification took place rapidly in rotted manure ; the addition of 5 per 

 cent of cellulose caused rapid denitriflcation. 



