502 STATE BOARD OF AGRICULTURE. 



Probably there are conditions that occur in the soil that can be studied 

 by means of the water extracts. These methods while obviously more 

 applicable for yielding data than extractions with acids and the like, 

 yield dilute washings from the soils which cannot be concentrated to 

 reproduce the original soil solution. 



3. Artificial Root. 



In their study of capillary movement of the soil moisture, Briggs and 

 McCalP tried to imitate the plant root in its absorption of moisture. A 

 close grained unglazed porcelain filter (Pasteur-Chamberland) was con- 

 nected to an exhausted 2 liter receiver and was so placed in the soil that 

 there would be good capillary connections. On account of the lower 

 pressure on the inside of the tube, the soil moisture was drawn through. 

 It is claimed that the solution tluis obtained is identical in concentra- 

 tion and composition with the soil solution from which plants get their 

 food. The disadvantage of this is that it is applicable only to those soils 

 of comparatively high moisture content and that it funiishes only a small 

 amount of solution. The adsorption on clay filters is known to be im- 

 portant enough to change seriously the solution obtained. 



4. Centrifuge. 



The method for obtaining the soil solution which is least open to criti- 

 cism is that developed in the Bureau of Soils. I quote from Bulletin 31. 



"Dr. L. J. Briggs and Mr. J. W. McLaue- of this Bureau have con- 

 structed for this purpose a centrifugal machine which consists of three 

 concentric cylinders, the middle one having fine perforations. The moist 

 soil sample as collected in the field, is put between the perforated mid- 

 dle cylinder and the inner cylinder. The system of three cylinders is 

 then rotated at a speed approaching 8,000 revolutions per minute. The 

 soil moisture is thrown through the perforations and collects in the 

 compartment formed by the perforated middle cylinder and the outer 

 cylinder. The solution is usually perfectly clear and needs no subse- 

 quent filtration. By this means it has been possible to reduce the soil 

 moisture to approximately the optimum condition for plant growth, and 

 this method of obtaining the actual soil moisture is therefore limited to 

 soils containing more than the optimum. Nevertheless, it has been pos- 

 sible to gain some valuable information concerning the actual concen- 

 tration of the free soil moisture by means of this method, although for 

 any extensive study the amount of solution that can be obtained is com- 

 paratively so small as to be practically prohibitive." 



5. Displacement Methods. 



A. Schloesing's method — Water. Historically this type of experi- 

 ment for obtaining soil solution is quite old. We find progressive develop- 

 ment in working out of this method. Among the first attempts to ob- 

 tain the soil solution in an unaltered condition was that of Th. KSchloes- 

 ing^ in the '60s. His first method dealt with 1 or 2 kgms but he then 

 modified this plan so as to admit the use of larger amounts of soil, 30 

 to 35 Kgms. An artificial rain of pure water was so produced that the 



^Briffffs, L,. J. and McCaU. J. R. : "An Artificial Root for Inducing- Capillary movement of 

 Soil Moisture." Science N. S. 20, (1904) pp. 566-8; Bui. 31, Bureau of Soils, U. S. Dcpt. of 

 Agr. (1901), p. 17. 



-Schreiner, O. and Failyer, G. II., Colorimctric, Turbidity and Titration Methods used in 

 Soil Investigations, Bnl. 31, Bureau of Soils, U. S. Dept. of Agr. (1905) pp. 16-17. 



'Schloesing, Tli. "Sur L'analyse des Principes solubles do la terre yogotable" Comntcs 

 Rendus de I'Academie des Sciences. 1866, 63, p. 1007. "Analyse des Eaux Conteneus dans 

 les terres arables" 1870, 70, p. 98. 



