SOILS FERTILIZERS. 423 



present knowledge of the subject. The author is of the opinion that colloid 

 investigations to date have been chiefly concerned with a study of pure adsorp- 

 tive processes, and that more attention should be given to the study of the more 

 important process, from the standpoint of soil and plant nutrition, of adsorp- 

 tion by exchange, and to changes in the character of colloids due to increase in 

 content of absorbed compounds and protective colloids. 



Bacteriological methods for the estimation of soil acidity, J. G. Lipman 

 (Science, n. ser., S3 {1911), No. 860, pp. 971-973).— This article notes the lack 

 of a satisfactory method for the quantitative estimation of soil acidity and 

 suggests the use of a method based upon bacteriological reactions. Preliminary 

 experiments are reported which show " that the amount of acid present in 

 cultivated soils may be determined quite accurately by comparing bouillon of 

 varying reactions with equivalent quantities of neutral bouillon containing 

 varying amounts of soil." The proposed method may utilize either ammonify- 

 ing, nitrogen-fixing, or nitrifying organisms. It is stated that a full report on 

 this subject is being prepared. 



Experiments on ammonia and nitrate formation in soils, J. G. Lipman, 

 P. E. Brown, and I. L. Owen {New Jersey Stas. Rpt. 1909, pp. 117-180).— Com- 

 parisons were made on various soils of the Remy and beaker methods of 

 studying ammonia formation in soils. 



The Remy method gave unsatisfactory results. In the beaker method " 100 

 gm. quantities of soil [were] thoroughly mixed with 0.5 gm. of peptone. At 

 the end of 3 or 4 days these portions of soil, kept in covered beakers and main- 

 tained at the same moisture content by means of sterile water, were transferred 

 to copper flasks and the ammonia was distilled off and determined." 



By neither method was there shown to be any direct relation between the 

 number of bacteria and ammonia formation, but " the methods employed were 

 capable of measuring with a fair degree of accuracy the differences in numbers 

 and nitrate formation." Further experiments indicated a relation between the 

 ammonia formed and the amounts of peptone, dried blood, and cottonseed meal 

 used in cultures. 



In a study of various factors affecting ammonia and nitrate formation it was 

 found "that the production of available nitrogen compounds is affected not 

 only by the amount of nitrogenous material present or applied, but also by the 

 depth of soil ; that is, the absolute quantity of soil in which a given quantity of 

 nitrogenous fertilizer is distributed." 



" In materials like cottonseed meal and dried blood the rate of decomposition 

 is affected up to a certain point by the volume of soil in which they are dis- 

 tributed ; that is, by variation in the physical, chemical, and bacteriological 

 factors involved. . . . The results emphasize in a practical way the impor- 

 tance of thorough distribution in the soil. We know that in field practice or 

 under market-garden conditions, even when relatively small amounts of nitrog- 

 enous materials ai-e used, the distribution may be so unsatisfactory as to bring 

 a comparatively small amount of soil in contact with a comparatively large 

 amount of fertilizer. Under such conditions the rate of ammonification and of 

 nitrification is likely to be affected in an unsatisfactory manner as indicated by 

 the present experiment." 



In continuation of previous experiments (E. S. R., 22, p. 120) showing a 

 certain periodicity in the accumulation of nitrates in soils, experiments were 

 made to show the effect on nitrification of adding varying amounts of nitrate 

 to the soil. The results showed "that the addition of sodium nitrate readily 

 affected the accumulation of nitrate nitrogen in the soil. When 0.2 gm. of 

 NaNOs were added the accumulation of nitrate was enhanced at the end of 2 

 7717°— No. 5—11 3 



