514 EXPERIMENT STATION RECOED. 



arbitrary standards of fertility of average European soils. Their mechanical 

 composition also is said to be unfavorable for cultivation. 



Methods for soil investigation, R. Albert and O. Bogs (Internat. Mitt. 

 Bodenk., 4 (1914), No. 2-3, pp. 181-198). — Comparative tests of methods for 

 determining the humus and water content and specitic weight of soils are re- 

 ported, the object being to determine the simpler and quicker methods which 

 are equally satisfactory for soils of different origin and history. 



For humus determination the simplified method of elementary analysis by 

 burning in a stream of oxygen, according to Dennstedt, is concluded to be the 

 most generally satisfactory. As regards water content it is concluded that with 

 sandy soils the determination by drying in an air bath at 105 to 106° C. is 

 sufficiently exact, while for loam, clay, and moor soils Schwalbe's method of 

 distillation with xylol is preferable. For specific weight determination is 

 preferred the simplified method of Wrochem, which is based on the principle 

 that pulverized and absolutely dry substances, such as cement, etc., are easily 

 freed of their air content by immersion in turpentine. 



The physical properties of soils, J. Kopeck y (Internat. Mitt. Bodenk., 4 

 (1914), No. 2-3, pp. 1.38-180, figs. 4)- — The author discusses the importance in 

 soil judgment of determining the physical properties of soils, draws attention 

 to the many inaccuracies in several of the commonly used methods, and de- 

 scribes methods and apparatus developed by him for determining the water 

 capacity, apparent and real specific weights, porosity, air capacity, and per- 

 meability of soils. 



It is concluded that the absolute water capacity of a certain type of soil in 

 nature, excluding all outside influences, may be expressed by the amount 

 z-etained after 24 hours following saturation, and that the air retained in the 

 remaining pore space serves to indicate the air capacity. On the basis that per- 

 meability is that property which permits the soil to retain its absolute capacity 

 of water and allow all excess to escape by percolation, relative permeability 

 is expressed as the quantitiy of water in cubic centimeters which will percolate 

 through a cross section of 100 sq. em. of a soil column 10 cm. high in 24 hours. 



The absorptive power of soils, P. Rohland (Biochcm. Ztschr., 63 (1914), 

 No. 1, pp. 87-92). — The author discusses the properties of soil colloids and 

 defends the colorimetric method for determining the absorptive power of soils, 

 particularly kaolin. The absorptive ix)wer of kaolin is said to be a measure of 

 its other properties, especially its plasticity. 



The nature of drought according to the evidence of the Odessa experi- 

 ment field, V. G. RoTMisTKOV (Sushchnost Zasukhi po Danny m Odesskago 

 Opytnago Folia. Odessa, Russia, Russian Ed., 1911, pp. 66, figs. 21; English 

 Ed., 1913, pp. 48, figs. 21). — A continuation of work begun in 1905 is reported 

 and results of previous investigations are summarized. The method of investi- 

 gation is described and laws of the circulation of water, the root systems of 

 plants in relation to the water of the soil, and methods of combating drought 

 are discussed. The conclusions reached are based upon over 60,000 determina- 

 tions of water in soils under different conditions of cropping and drought. 



The author separates the soil zone in which the roots of plants grow into 

 three layers, which are, beginning at the surface, (1) the periodically humid 

 layer variable in depth, (2) the intermediate dry layer extending to a depth of 

 from 63 to 71 in., and (3) the permanently humid layer below (2). He con- 

 cludes that water percolating beyond a depth of from 16 to 18 in. does not re- 

 turn to the surface except by means of the roots of plants, and that all water 

 not so utilized goes down into the deeper layers of the soil. 



Under normal conditions the network of roots is very uniform throughout the 

 soil layer which they occupy, but in order that this may be true and the 



