SOILS FERTILIZERS. 123 



in this respect as a soil layer 8.6 cm. thick. It is further shown that the 

 differences in range of temperature between soil covered with vegetation and 

 naked soil have a particular significance to the biology and geography of some 

 plants, especially the so-called Alpine plants. 



The use of dialysis and the determination of oxidizing power in judg-ing 

 soils, J. KoNiG, J. Hasenbaumer and K. Glenk (Landw. Vers. Stat., 70-80 

 {1913), pp. 491-534, pi. 1, figs. 2; abs. in Zentbl. Agr. Chem., 42 {1913), 'No. 5, 

 pp. 289-295; Jour. Chem. 80c. [London], IO4 {1913), No. 607, I, p. 578; Genthl. 

 Bakt. [etc.], 2. AM, 39 {1913), No. ^-7, pp. 18ft, i85).— Six different soils, 

 namely, sand, sandy loam, loam, limestone soil, clay soil, and schistose soil, were 

 subjected to dialysis, part in the natural state, part previously heated in a 

 vacuum to from 95 to 98° C, part heated to from 150 to 180°, and part treated 

 with hydrogen peroxid. After dialysis the amounts of organic matter, calcium, 

 magnesium, potassium, phosphoric acid, and sulphuric acid were estimated. 



The final results showed that only with dried clny soil did the quantity of sub- 

 stances obtained by dialysis fall below that of the natural soil. It was found 

 that soils heated to 150° yielded more soluble matter than untreated soils, 

 similar results, but less marked, were obtained with the soils dried at from 05 

 to 98°. The amounts obtained for sandy and sandy loam soils treated with 

 hydrogen peroxid were considerably higher than those obtained from natural 

 soils. From the results obtained, and since much time and considerable care 

 and accuracy are required, it is concluded that dialysis can have no practical 

 application in soil investigation. 



Clearer indications of the changes which soils undergo when heated and when 

 air-dried were obtained bj- estimating the electrolytic conductivity. The results 

 indicate that the ordinary drying out of soils produces a partial suspension of 

 the colloidal conditions and hence an increase in the solubility of the plant food 

 in the colloidal combinations. 



The amounts of carboh dioxid produced in six different soils and in the same 

 soils with small amounts of dextrose and urea were estimated daily for three 

 weeks. Contradictory results were obtained with and without dextrose, but at 

 a mean temperature of 15.7° the limestone soil formed the largest proportion of 

 carbon dioxid. At the end of this experiment the amounts of ammonia and 

 nitrates and the number of bacteria were estimated. Urea was almost com- 

 pletely nitrified in the loamy soil while the clay soil showed only very slight 

 nitrification. It was noted that the power of oxidation of a soil stands within 

 certain limits which can not be exceeded within a given time with a given 

 air supply. The addition of dextrose considerably increased the number of 

 bacteria in all the soils, in sandy soils as much as eightfold. The catalytic 

 power was affected in the same way except in the schistose and clay soils. 

 The electrolytic conductivity was increased by clay and diminished by dextrose. 

 It is concluded that determination of electrolytic conductivity is the best 

 method of disclosing the changes taking place in the soil and further that the 

 determination of oxidizing power is a very suitable method of investigating the 

 properties of individual soils. 



The results of pot exi^ermonts with oats showed that heating the soil at from 

 95 to 98° in a vacuum increased both the total growth and the mineral con- 

 stituents. From this it is concluded that alternate drying out and wetting of 

 the soil will promote the formation of soluble plant foods. 



The addition of dextrose and gum arable to loamy sand and loam diminished 



the yield of grain and straw. This is attributed to an excess of undecomposed 



sugar in the soil acting as a nonelectrolyte, impeding the movement of the ions- 



in the soil, or as a colloid shield restricting flocculation of the colloids. The 



28054°— 14 3 



