SOILS FERTILIZERS. 621 



;/. !>91). — This is a summary of a in-eliniinary report {livitiK the results of 

 numerous experiments which show "that tlie activities of anunonifyinu. nitrify- 

 ing:, deuitrifyiufr. iind nitroj:en-«allierinf: bacteria are different in soils from 

 what they are in solutions and that no adecpiate knowledjje of the efficiency 

 ip|' these A-arious soil organisms in effecting chemical change can be attained by 

 tests conductetl in solutions. Even the relative powers of different organisms 

 or of ditt'erent soils is largely affected by the conditions of the test. It seems 

 therefore that in the study of soil bacteria the work nuist be done with soils, 

 rather than with solutions, or at least that frequent controls or checks in soil 

 nuist bo made." 



Nitrification in acid soils. A. 1 >. Ham., N. II. .1. Mili.kr, and ('. T. GiMiNdiiAM 

 { I'roc. Ron. Soc. [London], Scr. B, 80 U90H), No. B 539, pp. 196-212; ahs. in 

 Jour. Soc. Clum. Indus., 27 (1908), No. 11, p. 581; Jour. Chcm. Soc. [London]. 

 9^ (1908), No. 5.'i8, II, p. 5.3//).— The more important features of this article 

 are .summarized as follows: " In the soil of certain of the permanent grass i)luts 

 at Kothamstetl. which is distinctly acid in consequence of the long-continued 

 use of ammonium chlorid and sulphate as manure, nitrification is greatly reduced, 

 and the nitrifying bacteria are only found siiaringly. In bulk, nitrification still 

 goes on slowly, despite the acidity of the soil. Water extracts of the soil 

 will not permit of nitrification unless they are previously neutralized. The 

 amount of nitrate produced would not be sufficient for the nitrogen taken up 

 by the croji, which must, in the main, utilize the ammonium salts without pre- 

 vious change. The acidity is chiefly due to sparingly soluble ' humic ' acids; 

 free hydrochloric and sulphuric acids are also present, bec-ause the soil extract 

 contains soluble acid in quantities comparable to the amount of chlorids and 

 sulphates also present, and to the anunoiiitnn suli)hate and chlorid annually 

 supplied as manure. 



"The acidity is not brought about by i)urely chemical or physical actions of 

 the soil upon the ammonium salts, but by various microfungi which are able to 

 remove ammonia from a solution of its salts and set free the acids with which 

 it was combined, the acidity attained in this way being equivalent to that of 

 the soil water on the acid plats. 



"The authors jittribute the continuance of the nitrification in these soils to 

 the irregular distribution of the materials comiK)Slng them ; though acid as 

 a whole, they still contain some calcium carbonate, each of the particles of which 

 f<irms a center for the nitrification process. The decline in fertility of the acid 

 jilafs may be attril)uted to the repression of the normal Itacterial activities of the 

 soil and the encouragement of the growth of molds." 



Nitrogen-fixing' bacteria. III, F. LiiiiNis and N. K. IMllai [Vrnthl. Bakt. 

 [ffc.l, 2. Aht., 20 (1908), No. 2ff-25, pp. 781-790; abs. in Chcm. Zt<j., 32 (1908), 

 No. 50, Rrpcrt., p. 323; Jour. Chcm. Soc. [London], 9.', (1908), No. 5 ',8, II, pp. 

 522, 523). — l{ei»<':'<iiig i»nd verifying work of other investigators, the atitbors 

 studie<l (1) tile most suitable culture solutions for nitrogen-fixing organisms, 

 (L't the effect of manuring on fixation, .iml C. ) variations in fixing jiower fmin 

 month to montli throughonf flie ycai-. 



The experiments were as a rule made hy inoculating IdU cc. of the culture 

 solutirm with 10 gm. of soil. 



Maunite and xylose were found In be the most ellicient sources of carbohy- 

 drates in nutrient solutions, Innnus tin- least etlicient. Manuring did not greatly 

 increase the rate of fixation, l»ut sujierpliosphafe was very elf(><*live in this 

 respect. TIh? cro|) yields varied (pnte uniformly with the rate of fixation. The 

 lixing i»ower of soils from plats varied from month to month during the year, 

 there being '2 maxima, one in the spring and another in the autumn. See also 

 previous w.irk ( K. S. H., 1!), p. ('.24). 



