SOILS FERTILIZERS. 319 



Omelianski, which it greatly resembles in all other morphological properties. 

 Cultures were made on the magnesia-gypsum disks of Omelianski and magnesia 

 disks of Perotti. As a substratum Omelianski's solution of salts with the 

 addition of varying quantities of extracts from dry leaves was used, and 

 ammonia was added in the form of the slightly soluble ammonium-magnesium 

 phosphate (NH* Mg PO4). 



The results of this preliminary work are summed up as follows: (1) Organic 

 matter in the form of soil, or of extracts from dry leaves or soil, exerted a 

 favorable influence on the growth of the nitrous organism on a solid substra- 

 tum, but an unfavorable influence in a liquid. (2) An increase of the precentage 

 content of carbonate of magnesia also exerted a favorable influence on the 

 growth of the nitrous organism. (3) Pure magnesium carbonate appeared to 

 be a very suitable substratum for the growth of the organism. 



On the decomposition of nitrates by bacteria, II, S. Severin {Vycstnlk 

 Bakt. Aghron. Htantzil V. K. Fcrraii, 190S. No. ./.}, pp. I.'i-.'i2). — The investiga- 

 tion reported was a continuation of earlier work by the author (E. S. R., 21, 

 p. 22) and dealt with 2 organisms, Bacillus pyocyancus and Vibrio denitriflcans, 

 the latter discovered by the author. The former report described a study of 

 these organisms in an artificial nutritive medium of a meat-peptone bouillon, 

 under aerobic conditions; the present report deals with studies of their life 

 activity under anaerobic conditions, and also with their denitrifying power in 

 the soil. 



The author gives data on the denitrifying activity of the organisms In nitrate 

 bouillon in an atmosphere of hydrogen and carbon dioxid. The denitrifying 

 process was found to be more energetic in an atmosphere of hydrogen than 

 under aerobic conditions. Carbon dioxid lowers considerably the activity of 

 the organisms, especially of T'. denitriftcans, but even in the latter case this 

 activity is still quite energetic. In the opinion of the author these organisms 

 as well as all denitrifiers, which decompose nitrates to free nitrogen, are aerobic 

 in their nature, but the denitrifying process excited by them is an anaerobic 

 process to a greater or less extent. For this reason there must be in the soil, 

 when well aerated by cultivation, an energetic multiplication of the denitrifiers, 

 but a feeble exercise of their denitrifying function, and conversely, in a soil 

 compacted and poorly aerated there must be a feeble multiplication of the 

 denitrifiers, but increased denitrifying activity. 



The author describes studies of the life activity of the 2 organisms in 17 

 samples of most diverse soils. It appears that the energy of multiplication of 

 the organisms in the soil depends directly upon the proportion of nutritive 

 substances in the soil. The more fertile the soil the greater the multiplication 

 of the denitrifying organisms. B. pyocyaiieus is the more energetic organism 

 and develops comparatively well even in poor soils; on the other hand, V. 

 denitrificans being less active multiplies only in good soils. The introduction 

 of manure and straw into the soil apparently intensified the life activity of 

 B. pyocyancus. both as regards its multiplication and its denitrifying power, but 

 did not seem to affect appreciably V. denitrificans. 



On the decomposition of nitrates by bacteria. III, S. Severin ( Vyestmk 

 Bakt. Aghron. Stantzii V. K. Fcrrcin, 1909, Xo. 15, pp. 37-53; Centbl. Bakt. 

 [e*c.], 2. At)t., 25 {1909), No. 19-25, pp. 47 9-Jf92).— The author here reports a 

 continuation of the above studies. 



In unfertilized clay soil these organisms in pure cultures produced almost no 

 denitrification, but when fertilizers were added denitrification not infrequently 

 became very marked. In chernozem soils the organisms produced no denitrifica- 

 tion whether fertilizers were added or not. When the soils were heavily 

 manured both organisms developed abundantly in the soil, but only one, B. 



