SOILS FERTILIZEKS. 519 



Tlie activity of nearly pure cultures of nitrate and nitrite organisms in steril- 

 ized sand or soil was increased by the addition of 0.02 and 0.05 per cent of 

 dextrose. Under similar conditions the activity of pure cultures of the nitrate 

 organism was increased by the addition of 0.05 per cent of dextrose. A supply 

 of carl)on dioxid is necessary for both the niti-ate and the nitrite organisms 

 whether dextrose is added or not. Carbon bisulphid retarded nitrification at 

 first, but afterwards increased it, probably as a result of stimulating action. 



Course of nitrification under the conditions of field experiments, S. Fkank- 

 ruRT and A. Dusciiechkin (Tijestiuk Saklt. Proniiiish., 1907; abs. in Zliur. 

 Oituitn, Agron. [Rnss. Jour. Erpt. Landw.], 8 (1907), No. 6, pp. 707, 70S).— De- 

 terminations of nitric acid and ammonia in the soils of fields of the Russian 

 Society of Sugar Manufacturers, which have been under experiment during a 

 number of years, ai'e reported, the object being to ascertain the influence of 

 barnyard and green manures on the course of nitrification. During the years 

 3903 to lOOG determinations were also made of nitrate and ammonia nitrogen 

 in soil planted to beets and in unplanted soil. 



Some of the main Tesults were as follows : An increased nitrification was 

 observed only on those fields on which the manure raised the yield. Large 

 quantities of straw manure did not lower the content of nitrate nitrogen in the 

 soil. Green manures lowered the content of nitrate and ammonia nitrogen in 

 the soil, and in this respect there seemed to be no difference between leguminous 

 and nonleguminous plants. The effect of the green manure is attributed to 

 changed moisture conditions resulting from the cultivation of green-manuring 

 plants. 



Periodic observations on the content of nitrate and ammonia nitrogen in the 

 soil showed these to be very variable, but no close connection between the varia- 

 tions of the nitrate and ammonia nitrogen in the soil was observed. The soil 

 not occupied by beets always showed a higher nitrate content than soil planted 

 tiv beets. This difference is accounted for not only by the consumption by the 

 plants of the nitrates of the soil but chiefly by the greater humidity of the soil 

 not occupied by the plants. 



The effect of carbonates upon nitrification, W. L. Owen (Georgia Stn. Bui. 

 81, pp. -i.2, i)ls. //, figs. //). — This bulletin discusses the importance and advan- 

 tages of nitrification in relation to plant growth. In view of the importance of 

 iiitrifieatinn (1) in supplying the plant with highly available nitrogen, and (2) 

 in preventing the loss of nitrogen from decomposing organic matter, the author 

 undertook investigations having as their object the discovery of the best means 

 of stimulating the activity of the nitrifying organisms. 



The investigations here reported dealt with "the extent to which nitriflcatioM 

 depends on the supply of carbonates present, and what forms of carbonates are 

 most conducive to nitrification." In order to determine these points series of 

 experiments were undertaken on (1) the effect of increasing amounts of car- 

 bonates on the nitrification of a given amount of ammonia; (2) the relative 

 values of potassium, magnesium, and calcium carbonate in their effect on nitrifi- 

 cation; and (3) the nitrification of an equal amount of ammonia in (a) ordi- 

 nary culture flasks, (b) special flasks so constructed as to admit of air deprived 

 of its carbon dioxid content, and (c) flasks to which carbon dioxid is supplied 

 in excess. 



" Pure cultures of the Xitrosomonas and Nitrobacter were obtained by in- 

 oculating with 3 gm. of garden soil a medium of the following composition : 

 Ammonium sulphate 1 gm., potassium phosphate 1 gm., magnesium carbonate 

 5 gm., distilled water 1,000 cc. This medium was sterilized by the intermittent 

 method for 15 minutes on each of three consecutive days. The flask containing 

 the inoculated medium was placed in an incubator and kept for several days at a 



