SOILS FKKTlLIZI'iUS. 17 



iiitrosPii-tixins I);u't(M'i:i. the iiilluciuv (if cni-lK)!! hisul]ilii(l in iiicrcnsiii.i; the yield 

 of crojis, frreeii iii.-imiriiif,'. solvent action of biuteria on phosiihatic fertilizers, 

 and a source of error in estinnitinj; the yield of cereals. 



The author's experiments show that the activity of the nitrogen-fixing bac- 

 teria is controlled more by the leniiierature of the soil than by the nutrient 

 materials avaiialile. for example, in s;)il supplied with sugai" and kept at a 

 lemi)erature of 7 ( '. there was no lixalion of nitnjgen. When, however, the 

 temperature was raised to 15, or bettor, 24°, there was rapid fixation of nitro- 

 gen. ^Moreovci-. in presence of substances such as sugar, which promote the 

 action of the denitrifying organisms, denitrification is more likely to prevail at 

 tlie lower temiieraturos than at the higher, liaising the temperature apparently 

 (>nables the nitrogen-tixing organisms to overcome the denitrifying organisms. 



Observations on. the effect of carbon bisulpliid on the organisms of the soil 

 indicate that the use of large quantities of this material does not prevent 

 (b'niti'iticatioii. a result which does not bear out lliltnev and StiiruHn-'s expla- 

 nation of the acti(ai of this substauee in increasing the yields of crops. 



Experiments are reported which show that the turning under of mustard as 

 a green manure resulted in a loss of nitrogen from the soil, the cause of which 

 was not ascertained. 



The author's investigations confirm those of Stoklasa in showing that soil 

 bacteria and other lower organisms produce acids in the soil which aid in dis- 

 solving and rendering assimilable the difficultly soluble phosphates. 



Data are reported to show that the api)earance of crops in the field is by no 

 means an accurate index of their actual yield when harvested. 



On the question whether nitrites or nitrates are produced by nonbac- 

 terial processes in the soil, E. J. Russell and N. Smith {.Jour. Ayr. 8ci., 1 

 {1H06), Xo. .'/, i)p. Ji'iJi-Ji')3). — The experiments reported in this article "were 

 made with a view to discover how far purely physical and chemical processes, 

 known to take place in the soil, may be expected to give rise to nitrites and 

 nitrates." They dealt with the possibility of the formation of nitrites and 

 nitrates during (1) the evaporation of water, (2) the oxidation of free nitro- 

 gen by catalytic processes and induced oxidation, and (3) the oxidation of am- 

 monia. The first dealt mainly with a study of Schiinbein's observations, fi'om 

 which he concluded that aunnoiiium nitrite is produced when water is evapo- 

 rated in air ; the second with the catalytic action of platinum black as studied 

 by Loew, ferric oxid as studied by Bonnema, humus, and soil ; and the third 

 with the oxidation of ammonia in the soil by catalytic action and induced oxida- 

 tion. 



The results as a whole are claimed to show conclusively that there is no 

 measurable formation of nitrites or nitrates in the soil from atmospheric nitro- 

 gen or from ammonia by chemical or physical processes and that under no cir- 

 cumstances does the evaporation of water produce ammonium nitrite. The evi- 

 dence as to the oxidation of free nitrogen by catalytic or induced oxidation 

 processi's in the soil is not conclusive, I)ut the results obtained in the experi- 

 ments rei)orted indicate " that if induced oxidation takes place at all its effects 

 are so extremely slight that in practice they would be altogether negligil)le. 



" Catalytic oxidation of nitrogen does not seem to occur in the soil. 



" Slightl.v different results were obtained with annnonia. As the higher oxids 

 of iron and manganese possess a slight ])ower of catalytically oxidizing ammonia, 

 it might be expected that soils in which they occur to any extent would possess 

 the same power ; in any case, however, the effect is only small, and appears to 

 be of no practical consequence. 



" Ou the other hand, ammonia oxidizes more readily in presence of other sub- 



