1917] SOILS FERTILIZERS. 121 



and corn stover gave a smaller effect than the manures, and the legume hays, 

 clover, and cowpeas showed the least effect on ammoniflcatlon of any of the 

 materials used. Increases in ammoniflcation due to the applications of humus- 

 forming materials were independent of the nitrogen-carbon ratio of the 

 materials added and were probably dependent on the chemical composition of 

 the substances. . . . 



" The dried-blood fresh-soil method gave better results for ammoniflcation 

 than the casein fresh-soil method. The latter gave better duplicate results, 

 but the differences between different soils were not nearly so pronounced. Some 

 further modification of the casein method seems necessary for its general use. 



" Nitrification was increased in much the same way as ammoniflcation, by 

 the various organic materials. The leguminous green manures exerted, how- 

 ever, somewhat greater effects than the manures, and also more influence than 

 the nonlegumes. These results were the opposite of those secured with ammoni- 

 flcation. but the differences were not great enough to permit of definite conclu- 

 sions. Increases in nitrification brought about by the various materials were 

 apparently independent of the nitrogen-carbon ratio in the substances. Indi- 

 cations of a greater effect of materials of a narrower ratio over those of a 

 wide ratio can not be considered conclusive. 



" Nonsymbiotic nitrogen fixation was favored by manure to a large extent. 

 Straw, stover, and nonleguminous hays had almost as great an effect as the 

 manures, and the leguminous hays had the least effect of any of the materials 

 used. The nitrogen-carbon ratio of the materials employed were of little or no 

 significance in indicating their effects on azoflcation. There were indications, 

 however, that nonlegumes and straws might increase azoflcation in soils to a 

 large enough extent to make their use more profitable than that of legumes, 

 which add nitrogen to the soil but are somewhat more expensive to use. . . . 



" Dextrose gave better results in the azoflcation experiments than mannit 

 and may, therefore, be substituted for the more expensive material. There 

 was little similarity between the effects of the different organic materials on 

 the different bacterial processes. . . . 



" The manures and legumes increased the flrst crop of oats, except in the 

 case of the horse manure, which apparently exerted an injurious effect on the 

 crop in its early stages of growth. . . . The substances with wide nitrogen- 

 carbon ratio decreased the crop yield while those of narrow ratios gave in- 

 creases. The nitrogen factor was evidently very important on this soil. 



"The nitrogen-carbon ratio of the organic materials did seem to be of im- 

 portance in determining the influence on the flrst crop of oats. . . . The in- 

 fluence of the various substances applied to the soils was noted on a second 

 crop of oats, but the relative effects were different. The nonlegumes had as 

 great an influence as the legumes, and hence previous conclusions are con- 

 flrraed that with the use of the former materials sufficient time must be 

 allowed to elapse for azoflcation to occur if as beneficial effects are to be se- 

 cured as with legumes. The nitrogen-carbon ratio of the materials applied to 

 the soil did not seem to be of as much importance in determining the effect on 

 the second crop of oats as in the case of the flrst crop." 



The organic matter of the soil. — IV, Some data on humus-phosphoric 

 acid, R. A. Gortneb and W. M. Shaw {Soil Sci., S (1917), No. 2, pp. 99-111).— 

 Studies of the phosphoric acid in the humus of soils described in previous 

 reports of this series (E. S. R., 37, p. 20) are reported. These included the 

 determination of the phosphoric acid content of the ammonia extracts of the 

 soils, of peats, and of unchanged vegetable materials both before and after 

 leaching the samples with 1 per cent hydrochloric acid. 



