40 SOIL SCIENCE [Bot. Absts., Vol. VI, 



SOIL SCIENCE 



J. J. Skinner, Editor 

 F. M. Schertz, Assistant Editor 



ACIDITY AND HYDROGEN- ION CONCENTRATION 



277. Blair, A. W., and A. L. Prince. The lime requirement of soils according to the 

 Veitch method compared with the hydrogen-ion concentration of the soil extract. Soil Sci. 9: 

 253-259. 2 fig. 1920. — Determinations were made of the lime requirement by the Veitch 

 method and of the hydrogen-ion concentration of the soil extract by a colorimetric method, 

 on plots of Sassafras loam to which varying quantities of limestone had been added. The 

 hydrogen-ion concentration of the soil extract decreased with increasing applications of lime- 

 stone, but not necessarily in proportion to the amount of limestone added. A fairly close 

 correlation exists between the hydrogen-ion concentration of the soil extract and the lime 

 requirement as determined by the Veitch method. Soils having a P H of 6.7 are alkaline by 

 the Veitch method. — W. J. Robbins. 



278. Demonlon, A. The reaction of soils, its determination and practical significance. 

 Rev. Sci. 58: 173-177. 1920. — Discussion and general review of work on soil acidity. — R. B. 

 Deemer. 



279. Joffe, Jacob S. Hydrogen-ion concentration measurements of soils in connection 

 with their "lime-requirements." Soil Sci. 9: 261-266. 2 fig. 1920.— The lime requirement of 

 soils showing about the same P H values is considerably higher for soils high in organic matter 

 than for sandy soils. In using the Veitch method a P H value of 6.6-6.8 of the solution before 

 evaporation indicates that the end point of the lime requirement by the Veitch method has 

 been reached. — W. J. Robbins. 



280. Wherry, Edgar T. The soil reactions of certain rock ferns. I. Amer. Fern Jour. 

 10: 15-22. 1920. 



281. Veitch, F. P. Report on the lime requirement of soils. Jour. Assoc. Official Agric. 

 Chem. 3: 371-374. 1920.— Report of progress.— F. M. Schertz. 



INFLUENCE OF BIOLOGICAL AGENTS 



282. Brown, P. E., and W. V. Halversen. Effect of seasonal conditions and soil treat- 

 ment on bacteria and molds in soil. Iowa Agric. Exp. Sta. Res. Bull. 56: 251-278. 1919. — 

 This study of the numbers of bacteria and molds in the soils of six differently-treated plots at 

 the Iowa Agric. Exp. Sta. throughout one full year showed that the bacteria decreased in the 

 late fall with lowering temperature, until the soil became frozen, when the number rose and 

 fell with the temperature regardless of the moisture. Upon thawing of the soil, the number 

 decreased but this was followed by an increase with increasing temperature and a maximum 

 number was reached on June 19 for all the cultivated plots and on April 12 for the continuous 

 timothy plot. The maximum counts were obtained on February 12 and June 19 with inter- 

 vening minimum counts. During the summer and early fall, the bacteria did not develop 

 parallel with either moisture or temperature. Applications of peat depressed the bacteria, 

 manure and clover increased the number, while the continuous timothy plot showed the high- 

 est number, which may have been due to the topography of the plot. — The number of molds 

 in the soils varied from one sampling to another, but there was no apparent effect of tempera- 

 ture, moisture, or soil treatment. The actual number of molds ranged from 42,000 to 131,000 

 per gram of soil, on the average. The number generally amounted to one-fortieth to one- 

 fiftieth of the bacteria present. There was no apparent relation between the bacteria and 

 •molds. Three media were used in the work. Albumen agar gave the highest count of bacteria 

 with modified synthetic agar second and Cook's No. 11 third. In the case of the molds, albu- 



