193 



ami distinct from nitrification proper. Further information was supplied 

 l.y Man-hal in his demonstration of the intense oxidizing activities of B. mycoides 

 involving the formation of carbon dioxid and of ammonia. It was perceived at 

 the same time that the quantitative estimation of ammonia in the soil could lead 

 to no definite conclusion because of the further changes which ammonia undergoes 

 in the soil. The same may be said also of the quantitative estimation of nitrites. 



On the other hand, the determination of nitrates in soils kept under definite con- 

 ditions promised to give valuable information not only as regards the rate of decom- 

 position of the soil humus, but also as regards the availability of various nitrogenous 

 fertili/.ers. It is not surprising, therefore, to find in agricultural literature a vast 

 amount of data hearing on the formation and accumulation of nitrates in the soil.& 

 We owe to these investigations a broader point of view and a deeper insight into 

 condition.- .if <..il. climate, and cropping in so far as they affect the oxidation of 

 organic mutter in the soil. 



Tin- many intcre-iing facts brought to light by various nitrification experiments 

 served to emphasize, among other things, the necessity of distinguishing the indi- 

 vidual factor- more or less prominent in the formation of nitrates. It seemed evi- 

 dent that, apart from conditions of moisture and temperature, the process of nitri- 

 tieation is dirertly ufferted by at least three important factors, viz, the physical 

 ami chemical cnniputution of the inorganic constituents of the soil; the physical 

 ami chemical composition of the organic constituents of the soil; the character of 

 the nitrifying, and perhaps of other bacteria present in the soil. Without going 

 iteld, wo may note in this connection the interesting experiments of Withers 

 and Fraps.c 



We find, in the first place, decided differences in the rate of oxidation of sub- 

 stances like dried blood, cotton-seed meal, dried fish, tankage, bat guano, bone, 

 ami ammonium sulphate. Not only were these differences maintained, but they 

 were in more or leas close agreement with the corresponding differences brought 

 out by digestion tests and vegetation experiments. We find also that the same 

 nitro^enoii- .-ul-iaiicw were nitrified to a very unequal extent in different soils. <* 

 :n live different soils the proportions of nitrate nitrogen formed from 

 n-eeed meal under the conditions of the experiment were 4.4, 17.6, 22.9, 41.2, 

 and 54.8 JMT cent, respectively. Evidently there were wide divergences in the 

 phy-ical. chemical, ami Bacteriological make-up of these soils. 



Hut, intere-iini: ua are the facts just noted, we encounter in the work of Withers 

 and Frap- ' a fad which is even more significant in its bearing on the physiology 

 of nitrification, namely, that in different soils ammonium sulphate and cotton-seed 

 meal are not nitrified in the same order. The authors are therefore led to conclude 

 that there may exi.-i in tin- soil an organism or organisms capable of oxidizing or- 

 ganic matter (they should have said ammonia) directly to nitrites or nitrates. This 

 assumption has been strengthened since by the investigations of Kaserer,/ who 

 believe- he has fntiml an organism capable of changing ammonia directly into nitrate. 



It would hardly be safe to theorize too much with these meager facts as a basis, 



hut for our purpose we may accept them at their face value in so far as they tend 



to -h..w the need of differentiation in the study of decay processes. The nitrates 



nt in the soil at any time may be but a small fraction of the total amount ac- 



Bui. soc. beige microsc., 1893, p. 83. 



6 t'. S. Dept. Agr., Office of Experiment Stations, Bui. 194, p. 57. 



rth Carolina Agr. Exp. Sta., Bui. 176, p. 19. 



' North Carolina Agr. Exp. Sta., Report of the Chemist, 1902-3, p. 6. 

 e North Carolina Agr. Exp. Sta., Annual Report, 1901-2, p. 37. 



:trbl. Bakt. Para., 1906, 16 [2] :681. 

 7::';7:J Hull. li 09 13 



