[Pboc. KoY. Soc. Victoria, 20 (N.S.;, Pt. L, 1907.J 



Art. v. — The Movements of the Soluble Constituents 

 in fine Alluvial Soil. 



By ALFRED J. EWART, D.Sc, Ph.D., F.L.S., 



Government Botanist and Professor of Botany 

 in the Melbourne University. 



[Eead 13th June.] 



One of the faults of the chemical ainaly^is of the soil, as car- 

 ried out by the latest methods, is that it pays far too little at- 

 tention to the soil as a changeable matrix, and attaches too 

 much importance to analyses made usuailly from samples of soil 

 taken at one time of the year only, and sometimes only from 

 one, or at most two, layers of the soil. This applies even to 

 those analyses where the water-soluble and acid-soluble con- 

 stituents are separately distinguished. As to the so-called 

 " complete " soil analyses formerly so common, and still in 

 favour in some quarters, these have about ais much value to the 

 agriculturist as the destructive analysis of a pair of boots would 

 have to a shoemaker. 



In the soil, the constituents of plant food consist (a) of the 

 water-soluble constituents immediately available for use ; (b) 

 of the acid (hydrochloric) -soluble ones, representing plant 

 food, which may become gradually available in one to iseveral 

 years. The rest of the soil may practically be regarded as a 

 mere matrix, whose physical properties are of great impor- 

 tance, but whose chemical properties have little or no immediate 

 concern to the plant. The water soluble constituents are con- 

 centrated in the surface-adhesion films of water around the 

 solid particles and air bubbles in the t^oil, so that prolonged 

 washing is needed to x'emove them completely. The plant, 

 on the other hand, in case of need, can concentrate the dissolved 

 salts in the process of absorption, although when actively tran- 

 spiring, it usually absorbs them in more dilute form than they 

 exi^it in the soil. 



In any case, every shower of rain falling on the land must 

 tend to lower the percentage of dissolved matter in the surface 



