SOILS FEETILIZERS. 425 



aRreenient between the yields and the uiuonnt of pliosplioric acid dissolved by 1 

 per cent hydrochloric acid in the ratio of 100 pai-ts of acid to 1 of soil. 



Experiments are reported which show that by replacing a portion of the 

 phosphoric acid and potash of nntrient solutions used for the growth of A. 

 nigcr by soil extracts an indication of the amount and availability of phosphoric 

 acid in the soil may be obtained from the growth of the organism. 



The thermal effect of moistening the soil, A. Muntz and H. Gaudechon 

 { Com lit. Rend. Acad. Sci. [Paris}, 1'i9 (1909), A'o. 6, pp. 377-381; Rev. Gen. 

 Agron., n. scr., // (1909), No. 10, pp. 3So-389 ; abs. in Chcm. Zentbh, 1909, II, 

 No 2-'f, p. 2032). — Studies of the heat generated on moistening soils and various 

 other substances as indicated by M it seller lich (E. S. R., 17, p. S3S) are re- 

 porte<l. The apparatus employed by Berthelot in investigations in thermo- 

 chemistry was used in these experiments, which were made with various kinds 

 of soil and of mineral and organic substances. 



The results show that clay, humus, starch, and organic substances in general, 

 which evolve considerable heat in contact with water, evolve very little or none 

 in contact with other liquids, such as benzene. Eighty-eight per cent alcohol 

 was partially dehydrated when brought into contact with clay, humus, and 

 starch which had been previously dried. The thermal effects resulting from 

 the moistening of the constituents of the soils and of organic sul)stances are 

 very complex. The investigations reported show that these effects are produced 

 with great frequency in the superficial layer of the soil and may have an influ- 

 ence on the reactions affecting the growth of plants. 



The evolution of heat when dry soil is moistened, A. MtJNTz and H. Gaude- 

 chon (Ann. Inst. Nut. Agron., 2. sen, 8 (1909), No. 2, pp. 161-212, figs. 5; Ann. 

 8ci. Agron., 3. ser., // (1909), II, Nos. 5, pp. 393-400; 6, pp. Ji01-Ji-'i3, figs. 5).— 

 This is a moi-e detailed account of investigations briefly noted above. It gives 

 full data for studies not only on soils of widely different kinds but also on the 

 constituent elements of these soils as separated by mechanical analysis and on 

 various organic substances, the purpose being to determine what constituents 

 are responsible for the thermal phenomena observed. As a rule the soils and 

 other substances experimented with were dried at 110° C. 



The results led to the general conclusion that the evolution of heat when dry 

 soil is moistened is due to the fixation of the water by the very fine mineral 

 constituents of the soil and by the organic matter. The attraction for the 

 water is so strong in many cases that it is capable of removing water from 

 compounds in which it is apparently in chemical combination, as, for example, 

 88 per cent alcohol. 



In discussing the practical application of this phenomenon it is pointed out 

 that plants may be injured by the elevation of temperature resulting from a 

 fall of rain on a soil which has been subjected to strong sunshine. 



Irrigation investigations: Factors influencing evaporation and transpira- 

 tion, J. A. WiDTSOE (Utah Sta. Bill. 105, pp. 64, figs. S).— This is one of the 

 series of bulletins reporting irrigation investigations made by this station 

 (E. S. R., 20, p. 814), which had for their object "the study of the mutual 

 relations of plants, soils, and water, as these relations may indicate the most 

 economic use of water for plant production." 



The investigations reported in this bulletin were made entirely with pots 

 under controlled conditions, especially with reference to percolation of water 

 in the soil. The pots used were 2 ft. in diameter and 2* ft. deep, and they 

 were so arranged that irrigation water could be applied in three different ways, 

 by surface irrigation, subirrigation, and water standing near the surface. Four 

 different kinds of soil were used, (1) college loam, (2) clay, (3) sand, and 



31125— No. 5—10 3 



