LYNDE-DUPRE 



ON OSMOSIS IN SOILS 



113 



Similar calculations for the other soil constituents give the fol- 

 lowing results : — 



TABLE 3. 



Giving the efficiency of the soil constituents as semi-permeable membranes. 



Resistance of 0-02 N. K CI solution at 16°C=250 ohms. 



Conclusion. — The finer the soil grains in a soil constituent, the 

 greater the efficiency of the soil constituent as a semi-permeable 

 membrane, when used with a clay subsoil solution. 



Suggestions for further investigations 



The theory on which we have been working is as follows: — 

 It is possible that: — 



(1) soils act as semi-permeable membranes; 



(2) moisture moves through the soil by osmotic pressure. 



We have substantiated this theory only for a particular clay 

 subsoil and certain soil constituents, prepared in a certain way. It 

 remains yet to show whether the theory applied to soils under field 

 conditions. 



A theory, in the beginning, is valuable in so far as it suggests 

 further lines of investigation. We find this theory valuable in this 

 respect. If we consider the theory in relation to the ordinary 

 operations of cultivation we find it suggests many lines of investi- 

 gation. 



If subsoils act as semi-permeables membranes, any operation 

 which makes the concentration of the soil solutions in the surface 

 soil greater than that of the solutions in the lower soil should bring 

 about an upward movement of water through the subsoil by osmotic 

 pressure. Let us consider this in relation to the ordinary operations 

 of cultivation namely: tillage, drainage, the application of manure 

 and mineral fertilizers, the use of the soil mulch, and the operations 

 used in dry farming. 



