516 EXPERIMENT STATION RECORD. [Vol.43 



Tlie results iiulicate that " in the case of sandy soil with little organic mat- 

 ter, an adjustment of the reaction to neutrality, or any point desired, may be 

 accomplished very conveniently by the liydro!,';en-ion concentration method." 

 It is thought that this study " points toward a method for the deternlination 

 and adjustment of the soil reaction in sandy soils and possibly even in soils 

 with a high organic matter content." 



The relative absorption by soil of sodium carbonate and sodium chlorid, 

 T. H. Keakney (Soil ScL, 9 (1920), No. 4, pp. 267-273, fig. i).— Experiments on 

 the absorption of sodium carbonate and sodium chlorid by sand soil, conducted 

 by the U. S. Department of Agriculture, iH'e reported, in which the usefulness 

 of the electrical-resistance method of determining differences in the absorption 

 of different salts by a soil was tested. Solutions of sodium carbonate and 

 sodium chlorid, of concenti'ations ranging from 0.05 to 1 per cent, were added 

 to air-dry sand in sufficient quantity to supersaturate it slightly. 



It was found that when equal volumes of solutions of equal concentration 

 of sodium carbonate and of sodiinn chlorid are added to sand and the solution 

 and soil are allowed to remain in contact during several hours the electi-ical 

 resistance of the sand to which sodium carbonate has been added is much the 

 higher. Since the greater resistance in the case of sodium carbonate must be 

 due to proportionately greater withdrawal of the solute by the sand, it follows 

 that plants growing in soils to which equal quantities of the two salts have 

 been added are in contact with soil solutions of very unequal concentration. 



The results of the experiment indicate that the electrical bridge affords a 

 convenient means for determining the degi'ee to which different salts are with- 

 drawn from a solution which has been added to a soil. In the case of sodium 

 carbonate and sodium chlorid, equivalent solutions of which (at the concen- 

 trations ordinarily encountered in alkali soils) do not differ greatly in elec- 

 trical resistance, the bridge method permits direct comparison of the concen- 

 tration of the solution in soils to which these salts have been added. 



The injurious effects of potash and sodium salts on the soil structure 

 and their causes, O. Nolte (Jour. Laiidw., 67 (1919), No. /,, pp. 207-272, fig. 

 I). — The author reviews his own work and that of others on the subject, and 

 describes the equipment used in his studies. He found that an alkaline salt 

 caused an increase in soil density and that an acid salt increa.sed soil per- 

 meability. A neutral salt slightly increased soil permeability, but this gradually 

 decreased. 



Eft'ect of calcium sulphate on the solubility of soils, M. M. McCool and 

 C. E. Millar (.Jour. Agr. Research [U. S.'], 19 (1920), No. 2, pp. 47-5Jf).—ln the 

 study here reported, which is a conti-ibution from the IMichigan Agricultural 

 Experiment Station, " six different soils were treated with a saturated solution 

 of calcium sulphate. In one series of experiments the mass was transferred 

 to filter paper, permitted to drain, and then transferred to containers and 

 the rate of formation of soluble substances determined by means of the freezing- 

 point method. The treatment was found to have increased the solubility of 

 the soil to an appreciable extent. 



" In another series the amount of soluble material was reduced to a minimum 

 by washing with distilled water, and the residuary effects of the treatment on 

 the solubility were likewise determined. The calcium-sulphate treatment was 

 found to have resulted in a very large increase in the rate of formation of 

 soluble substances. The effects were great even when the soils were washed 

 the second time. Obviously the treatment results in changes in the composition 

 of the soil mass — in other words, a soil of different properties is formed. It 

 seems that it is possible to alter the composition of the soil solution, and that 

 whether such change will have any effect on plant growth or not or whether 



