SOILS — FERTILIZEES. 817 



possible those of practice ; and it may be said that the soil will give back, but 

 with great diflieulty and only after very heavy rainfalls, the ammonia and the 

 potasli retained. So long as rain falls slowly enough to prevent washing the 

 soil will absorb high quantities of water which will be stored in the soil and 

 subsoil, the latter remaining the reservoir of the cultivated soil. Tlie soluble 

 salts which are carried away will not be lost for plant growth. Surface ten- 

 sion and capillarity will bring them back to the surface. If rainfalls are 

 heavy and compress the surface of the soil, washing will begin and a certain 

 amount of cultivated soil w'ill be carried away, together with the manure it 

 contains." 



The adsorption of potassiiim by the soil, A. G. McCall, F. M. Hildebrandt, 

 and E. S. Johnston {Jour. Phijs. Chem., 20 (1916), No. 1, pp. 51-G3, figs. S).— 

 A resume of literature bearing on the subject is given, and experiments with a 

 sandy loam soil in its natural state and with the same soil when ground for 

 four days in a porcelain-lined ball mill are reported. The object was to deter- 

 mine the amount of potassium absorbed from percolating solutions of potassium 

 chlorid containing 62 and 78 parts per million of potassium. Tlie flow of the 

 solutions during percolation was maintained at the rate of about 50 cc. in ten 

 minutes. 



With the natural soil and the w^eaker salt solution, it was found " that the 

 first ten-minute contact of the solution with the soil reduced its concentration 

 from 62 parts per million to 40 parts per million. At the end of the second 

 ten-minute period the strength of the solution is further reduced to 36 parts 

 per million, but from this point the concentration of the solution rises until the 

 fifth and last fraction is reached, when the concentration is within three parts 

 per million of the concentration of the original solution. The amount of potas- 

 sium retained by the soil rises gradually to 233 parts per milliou of the dry 

 soil when 250 cc. of solution have passed through." 



With the finely pulverized soil and the stronger salt solution, it was found 

 " that the amount of potassium in the solution has been increased instead of 

 decreased by its contact with the soil." This is explained in part on the basis 

 that the soil gave up some of its potassium to the percolating solution, and in 

 part on the basis of selective adsorption "in which the solvent (water) is 

 adsorbed more rapidly than the dissolved potassium salt, with the result that 

 the percolate is more concentrated than the original solution." 



The absorption of the ultraviolet and infra-red rays by arable soil, J. F. 

 Teistan and G. Michaud {Arch. ScL Phys. et Nat. [Geneva], 4. ser., 39 {1915), 

 No. 3, pp. 270-273, figs. 2; ahs. in Internat. Inst. Agr. [Ro'ine], Mo. Bui. Agr. 

 Intel, and Plant Diseases, 6 {1915), No. 6, pp. 796, 797; Rev. Sci. [Paris], 53 

 {1915), l-II, No. 16, p. 376; Sci. Abs., Sect. A-Pliys., 18 {1915), No. 8, p. 4OI; 

 U. S. Mo. Weather Rev., 43 {1915), No. 10, pp. 510, 511; Chem. Zentbl, 1915, I, 

 No. 23, p. 1222). — Experiments on the absorbing power of calcareous, sandy, 

 clayey, and humus soils, when di"y and when damp, for the two invisible ends 

 of the solar spectrum are reported, in which the photographic method w^as 

 employed. The ultraviolet rays were isolated by filtering sunlight through a 

 quartz lens covered with a very thin film of silver. A Wood filter was used 

 for the separation of the infra-red rays. 



It was found " that infra-red light is much less absorbed by damp soil of 

 all four types than by dry and that the soils absorb these rays in the following 

 ascending order : Calcareous, clayey, sandy, and humus. The ultraviolet light 

 also is less absorbed by damp than by dry calcareous soil, but the difference 

 is less for sandy soil and becomes imperceptible in the case of Imnuis and clayey 

 soils. The intensity of absoi-ption is least in the case of calcareous soil, which 



