512 EXPERIMENT STATION RECORD. [Vol. 38 



the several solutions, also by means of phenolphthalein indicatoi-. The greatest 

 electrical resistance and faint color of the indicator is coincident with the 

 concentration giving a neutral reaction. 



" The quantities of lime required to neutralize the acid soils may be deter- 

 mined by computing the quantities of calcium osid necessary to add to the 

 acid-soluble calcium osid found in the soils to bring the ratios CaO : Fe203+ 

 AI2O3 to 1 : 1.3. The quantity of calcium oxid required by this factor method 

 corresponds closely to the quantities required when determined by means of 

 the indirect titration method, and it appears that the titration method is acc\i- 

 rate and convenient." 



The literature of the subject is reviewed and a bibliography is given. 



Soil solution obtained by action of a hydraulic press, G. Ramann, S. Marz, 

 and H. Baueb (Internat. Mitt. Bodenk., 6 (1916), p. 27; Zentbl. Agr. Chem., .',6 

 (1917), p. 6; abs. in Jour. Chem. 80c. [London^, 112 (1917), No. 655, I, pp. 311, 

 312). — The authors point out that the analysis of drainage waters from soils 

 does not afford an accurate means of determining the composition of the normal 

 soil solution, as drainage only occurs when the soils are supersaturated. For 

 this reason they adopted the method of forcing water out of the soil with a 

 hydraulic press. Samples of 3 kg. of soil were taken from the fields and sub- 

 jected to a pressure of 300 kg. to the square centimeter, the liquid expressed 

 being then analyzed for calcium, magnesium, sulphates, phosphoric acid, and 

 potassium. The sampling was done on six different occasions over a period 

 lasting from May to October; both surface and subsoil were used. 



The calcium content was found to vary considerably in the surface soil, but 

 in the subsoil it seemed fairly constant, except for a rise in midsummer. 

 Potassium, contrary to the generally accepted view, behaved very much like 

 calcium, that is, its content fluctuated according to the general concentration 

 of the soil solution, rising when evaporation took place and being lowered by 

 spells of wet weather. Fui'ther, there was evidence of potassium and calcium 

 being transported from the subsoil to the surface during a prolonged period of 

 drought, but no evidence was obtained that adsorption exei'ted any regulating 

 effect on the concentration of the soil solution. The exchange of bases only 

 occurred when the proportion which the dissolved substances bore to one 

 another was altered. 



The authors suggest that the selective action of the plant roots, by throwing 

 the soil solution out of equilibrium, would have a considerable effect in bring- 

 ing fresh supplies of nutrient substances Into solution. They state also that the 

 pressure method of obtaining soil water Is only applicable in the case of soils 

 made up of very fine particles or containing a considerable amount of humus. 



The classification of soils according' to the electrical conductivity of their 

 aqueous extract, B. von Howath (Internat. Mitt. Bodenk., 6 (1916), No. 4, pp. 

 230-236; abs. in Internat. Inst. Agr. [Rome], Internat. Rev. Sci. and Pract. 

 Agr., 8 (1917), No. 2, p. 195).— Studies on the electrical conductivity of the 

 water extracts of about forty soils including gray and brown forest soils, prairie 

 clay, black and brown steppe soils, salt soil, alluvial, and sandy soils are re- 

 ported to determine whether electrical conductivity of the water extract of soil 

 can furnish a criterion for soil classification. A great variation in electrical 

 conductivity of the extracts was found and the conductivity of the same soil 

 was changed after cultivation. Since electrical conductivity of the aqueous 

 soil extract represents only the relative content of soluble salts it is considered 

 of no value for soil classification. 



Soil survey of Pickens County, Ala., A. M. O'Neal, jb., J. L. Andbess, J. M. 

 MooBE, and E. H. Stevens (U. S. Dept. Agr., Adv. Sheets Field Oper. Bur. 



