22 EXPERIMENT STATION RECORD. [Vol.40 



in understanding the possible mechanism in the reaction between soils and 

 soluble salts or their ions. 



" Considering all the evidence as a whole and from ever}* angle, it appears 

 that the water which refuses to freeze at the temperature of — 78° and has 

 been termed combined water, and which bears a close relationship to the heat 

 of wetting, exists partly as water of hydration and partly as water of solid 

 solution, with probably the former predominating. It may exist all as water 

 of solid solution but not all as water of hydration. On the other hand, if we 

 accept the recent theory that all interatomic or intermolecular forces should 

 be regarded as strictly chemical, which includes such forces or phenomena 

 as surface tension, evaporation, cohesion, absorption, condensation, etc., then 

 all the combined water is chemically combined. 



"The results obtained by the dilatometer method and those in the present 

 investigation seem to necessitate a complete and radical change of many of the 

 present conceptions regarding soil moisture. The present ideas regarding the 

 forma of water in the soils, the movement of moisture in the soils, the rate of 

 evaporation of the soil water, the available and Donavailable moisture in the 

 soil, must all be changed. The necessary changes proposed in the present paper 

 appear very reasonable and sound. It is now confidently believed that the dila- 

 tometer method is able to give a very accurate and true value of the wilting co- 

 efflcient of soils. It accomplishes this with great rapidity and facility. And 

 the value it yields is more definite and more comparable than that obtained by 

 the use of plants." 



The effect of drainage on soil acidity, S. D. OONRXB (S<i<juc. n. ter., 46 

 (1917), No. 1188, p. 846). — Examinations of samples of silt loam soil very low 

 in organic matter and quite acid, from contiguous drained and ondrained areas, 

 showed that acidity as determined by the potassium nitrate method had been 

 distinctly reduced by drainage. 



The phosphoric acid and potash requirements of meadow land as indicated 

 by analyses of the harvested material, P. Lit < hti and E. Kuteb [LandlO. 

 Jahrb. Schwete, SI (1!>17). No. 5, pp. 533-553).— Considerable tabulated data are 

 presented showing the phosphoric acid and potash content of dried material cut 

 at three different times during the year from numerous meadows in an effort 

 to ascertain the needs of the soil with respect to these two elements of plant 

 food. Analyses of the first cutting appeared to give better results than those <>f 

 either the total dry matter produced per year, or the second and third cuttings. 



It was concluded that an index to the soil requirements could be obtained 

 by determinations similar to those described, especially if the harvested 

 material was particularly rich or particularly deficient in either potash or 

 phosphoric acid, or both. 



Soil aldehydes, J. J. Skinner (.four. Franklin Inst., 186 (1918), Nos. 2, pp. 

 165-186; 8, pp. 289-316; 4, pp. 449-480; 5, pp. oJ7-5S4; 6. pp. 723-7)1. pi. 1. figs, 

 70). — This article reports the results of "a scientific study of a new class of 

 soil constituents unfavorable to crops, their occurrence, properties, and elimina- 

 tion in practical agriculture." 



It is shown that aldehydes form an important group of the organic com- 

 pounds in soils and that they are harmful in varying degree to plant growth as 

 shown by water cultures, pot tests, and field experiments. Their harmfulness 

 is variously modified by the character and condition of the soil and by drainage 

 and fertilizing. Salicylic aldehyde and vanillin are common, particularly in 

 unproductive soils. Their harmfulness is rapidly overcome or destroyed in 

 fertile, biologically active, and strongly oxidizing soils. Drainage, liming, and 

 certain fertilizers are effective correctives of toxicity due to aldehydes. 



An extensive bibliography of the subject is appended. 



