512 EXPERIMENT STATION RECORD. [Vol.35 



of which are taken to indicate that this soil is well supplied with potassittm and 

 phosphorus and that its potassium-sodium ratio is similar to that found in 

 limestone. 



Soil colloids, W. T. McGeobge {Hawaii Sta. Rpt. 1915, pp. 36, 57).— Atten- 

 tion is called to the invariable presence of colloidal aluminum hydroxid in 

 Hawaiian soils of high aluminum content. "In all soils which contain iron in 

 excess of alumina, this colloidal gel is never formed." 



Absorption and solution of ammonium and phosphate salts, H. Steatmann 

 {tjber Absorption und Losungen von Ammonium uiid Phosphatsalzen. Diss. 

 Univ. Giessen, 1914, pp. 62, figs. 2). — The work of others bearing on the sub- 

 ject is briefly reviewed, and experiments with a number of soils of different 

 mineralogical origin and composition, including loamy alluvial soils poor in lime, 

 clay, loess, blow sand, stony loam poor in lime, ortstein, marly soil, slaty clay 

 soil, sericite, slate soil rich in potash, weathered gray wacke soil, weathered 

 granite soil, diabase soil, weathered phonolite, basaltic soil, and diluvial sand 

 soil are reported. The purpose was to determine the extent to which the 

 absorptive power of a soil for ammonia and phosphates is influenced by decreas- 

 ing its content of colloidal material. Solutions of ammonium chlorid and 

 sulphate of concentrations equivalent to 200 cc. of nitrogen per 200 cc. of solu- 

 tion and solutions of monocalcium phosphate, dicalcium phosphate, and diam- 

 monium phosphate of a concentration equivalent to 492 mg. of phosphoric acid 

 per 400 cc. of solution were used. 



It was found that in mechanical soil analysis the sedimentation of the fine 

 colloidal particles was not a function of the time or the size of the particle, 

 making the results obtained by the decantation method more or less dependent 

 on an unknown factor. The Schon process was found to be more reliable than 

 the decantation process and in modified form was more simple. The absorptive 

 powers of soils of different origin and composition were influenced in a varia- 

 ble manner by the removal of the finest particles, according to the kind of spar 

 sand present. The silicon dioxid present in some basaltic soils, especially in 

 the group of particles of a diameter varying from 0.05 to 0.03 mm., was 

 found to be a new formation from the weathering of bauxite. The compo- 

 nents of so-called double silicates were found only in small amounts in many 

 soils of noteworthy absorptive powers. Synthetic silicates could not be char- 

 acterized as double silicates. Chabazite and stilbite minerals of the zeolite 

 group were found to be acid salts. Kaolin, as an acid aluminum silicate, is 

 considered to be fundamentally different from the amorphous aluminum sili- 

 cates of the soil. The main substance partaking in soil absorption and ex- 

 change of ions is considered to be amorphous aluminum silicate, which is the 

 end product of the normal weathering of feldspar. 



The influence of a stand of trees on the content of dissolved salts in an 

 upland moor soil, E. Ramann and H. Niklas (Ztschr. Forst u. Jagdw., 48 

 {1916), No. 1, pp. 3-11). — Two years' tests of the concentration of the solutions 

 of an upland peat moor soil supporting a stand of birch, pine, and other trees 

 are reported, using the electrical conductivity method. 



It was found that the soluble salt content of the forested soil was generally 

 larger than that of the bare soil and was less only in the fall. The variation 

 in salt content of the soils was the same for both years. The salt content was 

 rather low in May, Increased until July, and then decreased until September. 

 It increased in November to its greatest height. Laboratory tests of the dead 

 leaves led to the conclusion that the rise in salt content in the soils in Novem- 

 ber was due to leaching out of the soluble salts in the dead leaves. 



