210 SOIL SCIENCE [BoT. Absts., Vol. X, 



several types of Rothamsted soils. He has elaborated colorimetric methods for the estimation 

 of phenol and cresols which indicate an instantaneous loss of phenol followed by further loss, 

 slower and different in character. Phenol and the 3 cresols disappear with more or less ease 

 from all soils examined. The slow disappearance seems to be largely due to microorganisms 

 though evidence is adduced to show that some non-biological factor is in part responsible. 

 In soil autoclaved at 130°C. for 20 minutes no disappearance takes place, but the action pro- 

 ceeds slowly in the presence of considerable amounts of toluene or mercuric chloride. Soils 

 partially sterilized by toluene, which is removed by evaporation, are dephenolized more 

 rapidh' than ordinary soils, but steaming does not result in such an increase in rate. De- 

 phenolization takes place slowly in air-dried soils. It was found that successive doses of 

 phenol or m-cresol disappeared at increasing rates — a result which is regarded as pointing to 

 an action mainly biological in character. Two types of bacteria have been isolated from soil 

 which are able to decompose phenol in culture solutions containing mineral salts and phenol, 

 and a 3rd capable of decomposing m-cresol. Three types of dephenolization are recognized: 

 A biological type, an instantaneous chemical or physical type, and a slower chemical or physi- 

 cal type; the mechanism of the latter 2 types has not been elucidated. — V. H. Young. 



1380. Smith, R. S. Some effects of potassium salts on soils. Cornell Univ. Agric. Exp. 

 Sta. Mem. 35. 567-605. 1920. — The work was designed to show the effect of common fertili- 

 zer salts of potassium upon the growth of wheat plants and upon bacterial activities. Silt 

 loam of the Hagerstown, DeKalb, and Volusia series were used; in some cases lime was applied. 

 Data are presented on the grain and straw from crops grown upon the soil and from plants 

 grown in water extracts of the soils. These indicate that potassium chloride became toxic 

 at 1000 pounds per acre with Hagerstown soil and at 2000 pounds with DeKalb soil. Potas- 

 sium sulphate increased growth in both of these soils and no toxicity was noted with an ap- 

 plication of 3000 pounds per acre. — Under these treatments potassium chloride reduced the 

 accumulation of nitrates, as determined by the phenol disulphonic method, while potassium 

 sulphate exerted a stimulating eft'ect on nitrification; in DeKalb soil the greatest stimulation 

 occurred with 1000 pounds per acre. A study of the interchange of bases showed that both 

 potassium chloride and potassium sulphate replaced calcium markedly. JManganese was 

 replaced in very appreciable amounts in Hagerstown and DeKalb soil. The soil highest in 

 water-soluble manganese showed the least nitrifying efficiency, the smallest growth of wheat 

 in pot cultures, and the poorest growth of wheat rootlets in extract cultures. No iron or 

 aluminum was found in any of the water extracts. — /. K. Wilson. 



1381. Thomas, M. D. Aqueous vapor pressure of soils. Soil Sci. 11:409^34. 5fig. 1921. 

 — A dynamic method of measuring aqueous vapor-pressure lowerings of soil accurate to 0.01 

 mm. of mercury at 25°C. is described. The vapor-pressure-moisture curves are hyperbolae 

 over a wide range of moisture contents. Correlations between the vapor pressure of the soil 

 and the following properties are given: Hygroscopic coefficient, wilting coefficient, moisture 

 equivalent, "solid water," capillary potential, surface tension, and curvature of the mois- 

 ture surface. — 17. J. Robbins. 



1382. TuRPiN, H. W. The carbon-dioxide of the soil air. Cornell Univ. Agric. Exp. 

 Sta. Mem. 32. 315-361. 1920.— The CO2 content of air in Dunkirk clay loam was studied by 

 obtaining samples of the air by aspiration; after absorption of the CO2 in Ba (OH) 2 the excess 

 hydroxide was titrated with standard oxalic acid (the equivalent of the latter in terms of 

 CO2 having been determined by titrating with standard KMn04 solution). Two crops of 

 oats and 1 of millet were grown in the soil, the latter contained in large cans; some cans were 

 kept free from vegetation. The CO2 content of the air from the cropped soil increased as the 

 crops approached their greatest growing period; fluctuations were noted which were thought 

 to be due largely to temperature and pressure variations. High pressures were accompanied 

 by low CO2 contents while high temperatures resulted in high CO2 production. Some posi- 

 tive correlation seemed to exist between the amount of water percentage transpired and the 

 per cent of CO2; this was noted at a period during which the plant growth was most vigorous. 

 From this and other data presented it is concluded that the increase in CO2 in the cropped 

 soil was due largely to the respiratory activities of the plant roots. — J. K. Wilson. 



