594 STATE BOARD OF AGRICULTURE. 



tiraate contact with the surfaces of the soil grains would be more con- 

 centrated at any given time than the capillary or interstitial water, 

 due to the slow rate of diffusion, and if only the interstitial water is 

 extracted then the concentration of the extract would be less than that 

 of the entire moisture existing in the soil. Furthermore, since the soil 

 is a mixture of different minerals and the rate of diffusion is extremely 

 slow, especially in the soil system, the different mineral particles would 

 have films of different concentration, and if not all of these films are 

 extracted or trul}^ represented in the extract, the latter, of course, 

 would not possess exactly the same concentration as the entire soil 

 moisture. Again, due to the phenomenon of adsorbtion it has been sug- 

 gested that that portion of the moisture immediately at the surface of 

 the particles is more concentrated than the bulk of the solution. Whether 

 or not this last concept isi true cannot be proved; but it would seem 

 that when a substance, be it liquid or solid, is adsorbed, becomes inop- 

 erative or inactive. (3). There is no excellent reason to believe that 

 the solution obtained from a saturated soil will have both the same 

 concentration and composition as the moisture of the soil short of 

 saturation. 



The paraffin oil method consists of replacing the excess of soil water 

 with paraffin oil under pressure or suction. This method has been de- 

 veloped by Van Suchtelen and Itano (5), and Morgan (6), and is a 

 modification of Ischerekov's method, (7), wherein he employed alcohol. 

 Although a complete report of the results obtained by this method has 

 not yet appeared, it would appear, however, from many theoretical 

 principles as well as from some preliminary data already published 

 (6), that this method is capable of extracting only a limited amount of 

 the soil solution present in the soil and especially in the heavy types 

 of soil and, consequently is open practically to the same objections 

 as the centrifuge method. 



From the foregoing brief exposition of the different methods now in 

 vogue for studying the soil solution, it becomes very obvious that none 

 of them is capable of .furnishing definite information, either as to the 

 actual concentration or composition of the natural soil solution as it 

 exists in the soil under different conditions, including variation in 

 moisture content, season, tillage, fertilizer treatment, etc. Nor does it 

 seem possible or hopeful that they will ever be able to attain this object 

 so long as their principle is based, upon isolating the natural soil solu- 

 tion from the soil. From mechanical principles alone it would seem 

 hopeless to expect to ever execute a complete separation between liquid 

 and solid phases of the soil, or even a partial separation at the lower 

 magnitudes of water content. 



The next logical course that would suggest itself for obtaining a 

 more definite information, either as to the actual concentration or com- 

 position of the natural soil solution, is to study the latter in the soil 

 itself. Such study should give all the information desired and ought 

 to be devoid of all the objections applicable to the other methods. Any 

 method, therefore, capable of furnishing such definite information, either 

 as to the concentration or composition, or both, of the natural soil solu- 



(») Journal f. Landw. Band 60. Seite 369-370, 1912. 



(') Michigan Board of Agriculture Reports, 1913, p. 149, and 1914 p. 210. 



(') Russian Journal f. Landw. 8, 1907, No. 2 147-66. 



