122 EXPERIMENT STATION RECORD. 



in Jour. Chem. Soc. [London], 104 (1913), No. 611, I, p. 1035).— An electrical 

 method and apparatus for determining the reaction of soil extracts are de- 

 scribed and tests of the method on different kinds of soil are reported. 



Alkaline reactions caused by acids and their acid salts in soils, G. Masoni 

 (Staz, Sper. Agr. Ital., 46 (,1913), No. Jf, pp. 2^1-273; abs. in Chem. Zentbl., 

 1913, I, No. 2It, p. 1999; Jour. Chem. Soc. [London], IO4 (1913), No. 611, I, 

 p. 1036; Chem. Abs., 7 (1913), No. 19, p. 538i).—" Organic and mineral acids 

 and their acid salts are able to cause an alkaline reaction in soils. In calcifer- 

 ous soils calcium carbonate is formed, which in aqueous solution, on the addi- 

 tion of acid, parts with hydroxyl. The alkaline reaction may also be due to the 

 action of acids on basic salts of magnesium, calcium, or aluminum. Acid alkali 

 salts will give rise to alkali carbonates. The influence of the alkaline reaction 

 on the biological function of the roots is discussed." 



The chemistry of humus, with special reference to the relation of humus 

 to the soil and to the plant, S. L. Jodidi (Jour. Franklin Inst., 116 (1913) , 

 No. 5, pp. 565-573). — From a review of his own and other investigations the 

 author concludes, in opposition to the earlier idea that humus is made up of 

 but a few organic compounds, chiefly acid in their nature, that "more recent 

 investigations have thrown enough light upon the chemical nature of humus 

 or humus organic matter in the soil to demonstrate that it is a very complex 

 substance which, in addition to the dark-colored humin bodies, contains a large 

 number of organic compounds displaying acid, basic, neutral, and amphoteric 

 character." 



The value of humus in soils is attributed not only to the fact that it contains 

 most of the elements necessary for plant life but that it affords a means for 

 rendering more of the necessary inorganic elements available, improves the 

 physical condition of the soil, and in short " makes the soil a more habitable 

 and suitable home for the performance of the life functions of plants." 



The nature of humus and its relation to plant life, S. L. Jodidi (Biochem. 

 Bui., 3 (1913), No. 9, pp. 17-22). — This article is substantially the same as the 

 above. 



Observations on the influence of plant covering on soil temperatures, 

 J. Fkodin (Lunds Univ. Arsskr., n. ser., Sect. 2, S (1912), No. 9, pp. 16, pis. 4, 

 fig. 1). — Soil temperatures were observed in midwinter on snow-covered and 

 open soils, both fallowed and planted. 



It was found that on the coldest days the temperature at a depth of 10 cm. 

 under the plant covering was the same as at a depth of 17 cm. in fallowed soil. 

 The temperature at 10 cm. in the snow-covered soil was found to be equal to 

 that at a depth of 27.4 cm. in naked soil. Since the plant covering of from 2 

 to 4 cm. apparently had the same effect as a soil layer 7 cm. thick, and the 

 10 cm. snow layer the same effect as a soil layer 17.4 cm. thick it is concluded 

 that at the same thickness coverings of vegetation and snow would have the 

 same effect. After a thaw it was found that under the snow the top layer 

 of soil was warmer than a layer 20 cm, deep and that a still colder layer of 

 soil existed between these two. This is attributed to heat radiation through 

 the snow and is said to have a considerable biological and hydrographic in- 

 fluence. 



,A comparison of the daily ranges in temperature of soil covered with vege- 

 tation and fallowed soil showed that at 10 cm, depth the temperature range 

 of the former was only 55 per cent of that of the fallowed soil and that the 

 plant covering acted in this respect as a soil layer 9.1 cm, thick. Comparisons 

 of the daily range in temperature in the same soils on clear quiet days in the 

 late spring showed that the range at a depth of 10 cm, under vegetation was 

 only 59 per cent of that of the fallowed land and that the plant covering acted 



