SOILS — FERTILIZEBS. 517 



"The results here obtained seemingly contradict all previous work, for in the 

 series receiving manurial additions the sterile plates exceed the normal or 

 inoculated ones in the rate of evaporation. This is true in both cases where 

 manure was added. It is noteworthy, however, that the untreated series 

 showed an acceleration in the rate of evaporation iu the inoculated plates which 

 harmonizes witli the results of previous work." 



Addition of 2 per cent meal produced less effect than 1 per cent and addition 

 of 2 per cent manure reduced the evaporation due to bacterial activity. 



By means of a series of percolator tests there was found to be increased 

 capillary rise of moisture in the inoculated soil. It was also shown that evapo- 

 ration was increased by the gas formation due to bacterial activity in the 

 inoculated soil. 



The results of tests with soils inoculated with pure cultures of Azotobacter 

 and Bacillus subtilis confirmed those with soils containing mixed cultures, 



Tiie general conclusion is " that the soil bacteria and their activities are 

 factors which must be considered when discussing the movement of soil water ; 

 not so much because of the cells themselves as because of the by-products whicli 

 they form and the subsequent influence of the same upon such factors as surface 

 tension, capillarity, viscosity, etc., of the soil moisture. The biological feature 

 of the soil apparently forms an important contributory factor in determining 

 the movement of soil water." 



The nitrogen cycle in the soil, E. J. Russell {Chem. World, 1 (1912), No. 6, 

 pp. 185-187, fig. 1). — In this article the position is taken that most of the reac- 

 tions of the nitrogen cycle of the soil are bacterial. 



Studies in soil bacteriology. — V, The nitrifying and ammonifying powers 

 of North Carolina soils, F. L. Stevens, W. A. Winters, et al. (Centbl. Bakt. 

 [etc.], 2. Abt., 34 (1912), No. 8-9, pp. 187-203, figs. 13).— In continuation of 

 previous studies (E. S. R., 23, p. 721), tests were made of the nitrifying and 

 ammonifying power of samples of tj-pical soils from different parts of the State. 

 An attempt is made to correlate the results with the crop-producing power of 

 the soils. 



About 42 per cent of the soils showed no nitrification. It was as a rule more 

 active in soils which had grown legumes or had been manured than on soils 

 not so treated. No positive relation between nitrification and productiveness 

 was established. Ammouification was very variable. 



A summary of investigations on nitrogen fixation of Azotobacter chro- 

 ococcum, G. Rosing (Centbl. Bakt. [etc.], 2. Abt., 33 (1912), No. 25, pp. 618-- 

 623). — The work of T. Reniy and the author on this subject is summarized. 



The results of the investigations, which have been in large part reported 

 and noted from time to time, show that lime and magnesia increased the 

 amount of nitrogen fixed in Beijerinck's mannit solution by Azotobacter. Free 

 acid, which prevented any marked bacterial development, was neutralized by 

 lime or magnesia, thus enabling the organisms to utilize the carbohydrates 

 added as sources of energy. Mannit, sucrose, and dextrose in connection with 

 mannit, were especially favorable as such sources of energy. The gain in 

 nitrogen during a period of 6 weeks from additions of sucrose (2 per cent) 

 was 103 mg. per kilogram of soil. Tests showed that the nitrogen thus fixed 

 in the soil was a useful source of supply of this constituent to the higher plants. 

 About 32 per cent of nitrogen fixed in the soil was assimilated. 



Humus acids increased the fixation of nitrogen in nutritive solutions, the 

 maximum amount being produced for 0.1 gm. of humus acid per gram of 

 Beijerinck's mannit solution. The active constituent of the humus acid was 

 found to be iron. A solution of 1 gm. iron chlorid, 10 gm. cane sugar, and 0.8 

 gm. of sodium per liter was especially beneficial to the bacterial activity. 



