762 



SCIENCE 



[N. S. Vol. XXXVI. No. 935 



study of the ammonifying powers of some Col- 

 orado soils, among them some of the now well 

 known " niter soils " and some of the normal 

 soils of the state. In concluding the discus- 

 sion the author attempts a comparison of the 

 ammonifying powers of soils from different 

 states with his own, in which he quotes data 

 on the subject obtained by J. G. Lipman as 

 regards New Jersey soils, F. L. Stevens and 

 coworkers as regards North Carolina soils and 

 the writer as regards a California soil. From 

 the comparison Sackett concludes that the 

 niter soils of Colorado show a much higher 

 ammonifying eflSciency than soils from other 

 states and than the normal soils of Colorado. 



Despite the fact that Professor Sackett 

 makes some qualifying statements in discus- 

 sing the comparisons, he does not seem to at- 

 tach importance enough to some factors of 

 which he appears to be fuUy cognizant, and 

 gives no consideration to other very important 

 factors. The writer of this note fails to ap- 

 preciate the value of a comparison of the am- 

 monifying powers of various soils as obtained 

 by different investigators whose methods vary 

 as much as ours do to-day. Not only is it 

 true, as Professor Sackett points out, that the 

 time of incubation may be responsible for 

 some of the differences found between his 

 normal sandy loam and the one with which I 

 worked, but differences of great magnitude 

 can easily be obtained in changing the length 

 of the incubation period, as J. G. Lipman has 

 repeatedly shown in his long series of investi- 

 gations on ammonification at the New Jersey 

 Experiment Station. Moreover, the writer 

 has found different brands of dried blood to 

 vary so much in composition, both physically 

 and chemically, that no fair comparison can be 

 made without employing not only the same 

 period of incubation and the same tempera- 

 ture for all soils but also the same kind of 

 dried blood. 



Other important factors also militate 

 against a useful comparison of the ammoni- 

 fying powers of different soils as obtained in 



^Bull. No. 184, Colorado Experiment Station, 

 Part 1, June, 1912. 



laboratories varying widely in their methods 

 of studying such problems. For example. 

 Professor Sackett sterilizes his soils with 

 mercuric chloride and then rinses them with 

 sterile distilled water prior to inoculation 

 with a soil infusion. In my laboratory soils 

 are used directly for cultures without the use 

 of a soil infusion. Others may use either 

 procedure or both. I fail to see how one can 

 safely compare the flora of a soil in its natural 

 condition with a partial flora introduced 

 through a soil infusion. The act of sterilizing 

 a soil has been amply shown to be favorable 

 to nitrogen transformation, but if in addition 

 to that the soil is rinsed with water, it is ob- 

 vious that the culture medium may become 

 an entirely different one and yield a different 

 ammonification coefficient from the same soil 

 unsterilized or unrinsed. A soil infusion 

 equivalent to 5 grams of soil may give a very 

 far different bacterial development, possessed 

 of very far different powers from the whole 

 flora of 100 grams of soil. It must also be 

 added here that the comparison of only a few 

 soils can not be invested with much impor- 

 tance even if the soils are described by similar 

 names. It is of course obvious that sandy 

 loams may embrace soils of very widely dif- 

 fering natures and that no just comparison 

 can be made between a sandy loam so called in 

 one district with a sandy loam so called in 

 another district. 



As to the ammonification coefficients of niter 

 soils as compared with those of normal soils 

 the writer begs to add that he has on several 

 occasions noted a high ammonifying power in 

 soils of this state containing abnormal 

 amounts of nitrate and has attributed that 

 not only to a partial denitrification of the ni- 

 trate but also to an enormously increased de- 

 velopment of putrefactive organisms in these 

 soils which always produced large amounts 

 of ammonia. I have also noted the same thing 

 on two niter soils derived from the vicinity of 

 Grand Junction, Colorado. 



Chas. B. Lipman 



Labokatort op Soil Chemistry 

 AND Bacteriology, 

 University op California 



