222 SOIL SCIENCE [BoT. Absts., Vol. VIII, 



Pot experiments are of great value in accurate physiological experimentation but cannot be 

 used to solve many problems connected with fertilizers. Various systems of arranging small 

 plots and checks provide a method of compensating for the natural inequalities to be found in 

 ordinary plots. Systems in vogue in a large number of experiment stations are described. — 

 V. H. Young. 



1530. Stewart, G. R., and J. C. Martin. Effect of various crops upon the water extract 

 of a typical silty clay loam soil. Jour. Agric. Res. 20: 663-667. 5 fig. 1921. — The effects of 

 crops of maize, horse beans, potatoes, turnips, and barley upon the water extract of Yolo 

 silty clay loam was studied. Each crop reduced the concentration of the aqueous extract. 

 The nitrate content was reduced to a very low figure. — Concentration of soil solution is not 

 reduced significantly vmtil the portion of soil sampled is filled with roots. — D. Reddick. 



1531. Walker, Seth S. Chemical composition of some Louisiana soils as to series and 

 texture. Louisiana Agric. Exp. Sta. Bull. 177. 27 p. 1920. — The chemical analysis of 67 

 soils and 64 subsoils, representing 27 soil types in the Long Leaf Pine Belt of Louisiana, is 

 given together with a general discussion. — C. W. Edgerton. 



PHYSICAL INVESTIGATIONS 



1532. BouYOUCOS, George. Degree of temperature to which soils can be cooled without 

 freezing. Jour. Agric. Res. 20:267-269. 1920 [1921]. — Mineral soils may be supercooled to 

 — 4.2°C. without freezing; peats and mucks withstand— 5°C.; water, gelatin, agar, etc., may 

 be supercooled to— 6°C. No definite explanation of the phenomenon is offered but theo- 

 retical considerations are presented. "The ability of soils to resist freezing even when their 

 temperature is much below the freezing point throws considerable new light on [biological] 

 questions regarding the temperature of soils in cold seasons." — D. Reddick. 



1533. Comber, Norman M. The flocculation of soils. Jour. Agric. Sci. 10:425-436. 

 1920. — This is a study of the effect of calcium salts in the flocculation of soils. Silt is most 

 easily flocculated by calcium salts when the suspension is neutral. The addition of alkali 

 renders the flocculation more difficult. Soil "clay" behaves in an opposite manner and is 

 precipitated from alkaline suspensions more readily than from neutral ones. This behavior 

 suggests that of "emulsoid" colloids and it is suggested that clay particles are protected by 

 emulsoid colloids and so behave like them. If this is true, the action of lime is seen to be in 

 accordance with the known facts of colloidal chemistry. Clay as an emulsoid is conceived 

 to protect larger particles which are "suspensoid" in nature. Thus clay imposes its emul- 

 soid nature on soil aggregates and thus on the whole soil. Fine silts are lacking in "emulsoid" 

 clay to protect the larger "suspensoid" particles and are consequently not flocculated by 

 calcium hydroxide. — V. H. Young. 



1534. HoAGLAND, D. R., AND J. D. Martin. Effect of season and crop growth on the 

 physical state of the soil. Jour. Agric. Res. 20: 397-404. 1920 [1921].— "*rhe physical state of 

 certain soil constituents is influenced to a marked degree by the concentration of the soil 

 solution. The colloidal condition of the soil suspension undergoes significant alterations 

 during the season. A large increase in colloidal matter is noted when the soil solution is 

 depleted as a result of absorption of solutes by the plant." — D. Reddick. 



1535. Keen, Bernard A. The relations existing between the soil and its water content. 

 A resume of the subject. Jour. Agric. Sci. 10: 44-71. 1 fig. 1920. — A review of the subject, 

 with numerous citations, is presented. Emphasis is laid on the collodial nature of soil and 

 the necessity of attacking the problem of soil moisture from this point of view. — V. H. Young. 



1536. MoRETTiNi, A. Un decennio di ricerche suU arrabbiaticcio. [Ten years of study 

 upon the subject of "arrabbiaticcio."] Staz. Sperim. Agrarie Ital. 53: 146-171. 1920.— The 

 condition of the soil that receives in Italy the name of "arrabbiaticcio" and in France the name 

 of "terre-gatee" has been known in Europe since the time of the Romans and was described 



