1916] Sharp : Soluble Salts and Soil Colloids 333 



was more difficult to leach from the soil than NaoCOg or NaCl. 

 Specific information on the physical condition of the drained 

 alkali soils of the various drainage experiments is lacking. Even 

 the recorded observations of a general nature are indefinite and 

 discordant. Thus at Salt Lake,"^ Tempe/'^ and North Yakima,*'^ 

 the effect of drainage has not appeared to have benefitted the 

 physical condition of the soil, while at Fresno,*'*, Billings,*'^ and 

 elsewhere, the drained soil appeared to be superior with respect 

 to physical condition than the undrained soil. Owing to the in- 

 adequacy of these reports in that no definite measurements of 

 alteration in the physical condition of the soil are given, they 

 cannot be accepted as a final expression of the effects of drainage 

 of alkali soils. 



The behavior of the Davis soil in the cylinders and the general 

 trend of the laboratory experiments seem to the writer convincing 

 arguments that the drainage of these cylinder soils in their 

 present condition would be practically, perhaps absolutely, im- 

 possible. Underdrainage, supplemented with powerful flocculat- 

 ing agents, might serve ac a feasible plan whereby the excess salt 

 could be removed from such soils. 



That natural alkali soils are not strictly comparable with the 

 cylinder soils to which single salts have been added is patent, 

 and this may account, in a measure, for the general discrepancy 

 between the behavior of certain natural alkali soils and that of 

 alkali soils made artificially by the addition of salts. The wash- 

 ing out of salt mixtures, as in the case of natural alkali soils, may 

 have an entirely different effect than the washing out of a single 

 salt. It has, however, been shown in this laboratory that the 

 washing out of certain mixtures of salts from the Davis soil has 

 resulted in the same way as washing out single sodium salts. On 

 the other hand, the time for the reaction of the salt in the soil 



eiDorsey, C. W., U. S. Dept. Agric. Bur. of Soils, Bull. 43, p. 16, 

 1907, and Bull. 35, p. 181, 1907. 



62Dorsey, C. W., U. S. Dept. Agric, Bur. of Soils, Bull. 35, p. 190, 

 1907. 



63 Loc. cit., p. 189. 



64Mackie, W. W., U. S. Dept. Agric, Bur. of Soils, Bull. 42, p. 43, 

 1907. 



65Dorsey, C. W., U. S. Dept. Agric, Bur. of Soils, Bull. 44, p. 18, 

 1902. 



