SOILS FERTILIZERS. 29 



the origiu of the brown " niter spots " or excessive nitrate accumulations occur- 

 ring here and there in cultivated soils of Utah, Colorado, and Wyoming are 

 reported. 



Analyses of samples of the country rock contributing to the formation of the 

 soil, particularly shales and sandstones, showed them frequently to be heavily 

 impregnated with nitrate accumulations and quantities of other alkali salts 

 which wei'e in many cases equal to those occurring in the " niter spots " in 

 cultivated soil. A marked variation was found in the amount of nitrate pres- 

 ent, depending on the location in the geological series, the country rock richest 

 in nitrates being of Cretaceous and Tertiary origin. Uniformly high results 

 were obtained at widely separated sections. The sandstones and shales adja- 

 cent to the nonaffected areas were comparatively free from nitrates. 



The authors conclude that the nitrate accumulations in the cultivated soils 

 of the affected areas are derived from the nitrate deposits occurring originally 

 in the country rock and predict that "the so-called 'niter spots' may develop 

 and become troublesome in every section where Tertiai'y and Cretaceous rocks 

 are the chief source in the formation of the soil." 



The assimilation of the nitrogen of the air by free living lower organisms 

 in the soil, W. Schneidewind {KiUm Arch., 5 {1914), PP- 57-78, figs. 3). — 

 Comparative culture tests of the nitrogen-fixing power of different soil organisms 

 showed that Azotobacter is by far the most active of such organisms. In pot 

 experiments it was found that when sugar and straw were allowed to remain 

 for a sufficient length of time in the soil before planting the yield and nitrogen 

 content of plants grown in the soil were greatly increased. If,' however, the 

 planting was done soon after the application of these materials there was a 

 decline in yield and nitrogen content. The same results were observed in field 

 experiments. 



Ammonifying power of soil-inhabiting fungi, H. C. McLean and G. W. 

 Wilson (Science, n. scr., 40 (1914), No. 1021, pp. 14O-I42). — Comparative tests 

 were made by the beaker method of the rate of ammonificatiou of dried blood 

 and cotton-seed meal by various soil bacteria and fungi, the latter including 

 Zygorhynchus vuiUcminU, RMzopns nigricans, MoniUa sitophila, and certain 

 species of Penicillium, Alternaria, Aspergillus, Trichoderma, and Mucor. 



There was found to be considerable difference in the ammonifying power of 

 the various fungi. The largest ammonifying efiiciency was observed in the case 

 of Trichoderma, which showed 90.5 mg. of ammonia nitrogen out of a total of 

 155 mg. added in organic form in the test containing acid phosphate and 75.2 

 mg. in the test without addition of acid phosphate. The highest amount of 

 ammonia accumulated in the case of bacteria was with BociUus suhtilis, which 

 showed 54.1.3 mg. of ammonia nitrogen without acid phosphate and 17.55 mg. 

 with 2 per cent of acid phosphate. 



The environment of soil bacteria, F. H. H. van Suchtelen (Rpt. Mich. 

 Acad. 8ci., 15 (1913), pp. 65-70). — The investigations upon which this article is 

 based have already been noted from another source (E. S. R., 31, p. 317). 



Soil acidity, J. E. Harris (Michigan Sta. Tech. Bui. 19 (1914), PP- 3-15). — 

 The author reviews various opinions regarding soil acidity, briefly describes 

 some of the more important methods for its determination, and reports experi- 

 ments with acid upland sand and clay soils, using kaolin in a similar manner 

 for comparison. Jt is concluded " that the reaction of so-called acid soils of 

 the sandy loam type is one of selective adsorption by the soil of the basic con- 

 stituents of the neutral salt solution. It Is not due to a double decomposition 

 with adsorped acids or insoluble ' humic acids.' . . . 



"The 'acidity' of soils of the type investigate*! probably arises from the 

 formation of soluble salts through the interaction of weak acids (CjHsOi, CO2, 



