216 EXPERIMENT STATION KECOKD. 



found to be fairly rich in lime while the other two were comparatively poor, 

 especially the podzol. 



In tests of certain potassium-containing silicates as sources of available 

 potassium, biotite, muscovite, and nepheline when treated with ammonium 

 chlorid and barium chlorid showed relatively large quantities of available 

 potassium while orthoclase, sanidin, microclin, and leucite were very poor in 

 this respect. However, it is stated that a quantitative comparison can not be 

 made by these results since the different potassium silicates and zeolites are 

 said to be in variable states of stability regarding potassium. An artificial 

 sodium zeolite was treated with potassium and ammonium chlorids in order to 

 get the corresponding potassium and ammonium zeolites. Pot tests with buck- 

 wheat of these and other silicates showed that the potassium in the zeolites, 

 as also in the biotite and nepheline, was largely in available form, but this 

 was not so when the zeolites were protected from contact and reaction with the 

 other plant food salts, a strong fixation of the potassium being apparent. In 

 this case the addition of calcium carbonate worked satisfactorily in converting 

 the potassium compounds into available form as did also mixtures of the salts 

 of other foods. 



The so-called isolation method was used to test the effect of the various 

 silicates when not in contact with other plant food compounds in the soil. 

 In this method two concentric cylinders are used, the inner being much smaller 

 and somewhat shorter than the outer. Some of the roots of the plant are placed 

 in the inner cylinder which is filled with sand containing only the silicate to 

 be tested. The rest of the roots are allowed to grow in the sand which fills the 

 outer cylinder to the top and is supplied with all necessary elements of plant 

 food except that added to the inner cylinder. The top of the latter is closed 

 so that there is no interchange of plant food between the cylinders. In this 

 way the plant was forced to draw its potash supply from the silicate in the 

 inner cylinder without the aid of the solvent action of other fertilizing sub- 

 stances. 



Experimental investigations on the question of precipitation of iron in 

 podzol soils, B. Aarnio {Internat. Mitt. Bodenlc, S {1913), No. 2-3, pp. 131- 

 IJ^O), — Experiments made to determine the movements of iron in podzol soils 

 showed that it moves in such soils in ferrous forms reduced from ferric salts by 

 humus solutions and as iron colloid solutions in soil solutions which are poor in 

 electrolytes and show a high humus content, as is the case in sandy podzol soils. The 

 iron sinks into the deeper layers of such soils and forms ortstein when conditions 

 are favorable for precipitation. It is also shown that iron can be precipitated 

 by electrolytes, of which sulphuric acid and silicic acid are the most prevalent 

 in this soil, and by colloidal silicic acid and humus. The electrolytes and col- 

 loids are said to effect precipitation only within fixed limits of concentration of 

 the solution to be precipitated. The colloid iron is said to diffuse through the 

 upper part of the soil and is there precipitated by humus and electrolytes. This 

 explains the presence of so much iron in the upper layers of podzol soils. 



Iron in the ground water in the form of salts of mineral acids rises through 

 capillarity and is precipitated in the upper layers of the soil. 



Work of the chemical laboratory of the Ploti Experiment Station, 1912, 

 S. SKAi^Kii {Godichnyi Otchet FlotL Selsk. Khoz. Opytn. StantsU, 18 {1912), 

 pp. 133-221, 349-380, pis. 3). — The work reported included bacteriological as 

 well as chemical studies of the soil. The intensity of the process of the fixa- 

 tion of nitrogen in the soil under different cultural conditions; the intensity of 

 the processes of nitrification aiid denitrification in tilled and untilled fallow; 

 and the conversion of easily soluble phosphoric acid into insoluble form under 

 the influence of chemical and microbiological factors were studied in field and 



