334 University of California PubUcations in Af/ricHltin-al Sciences [Vol. 1 



being comparatively unlimited in case of the natural soils, it may 

 considerably alter the end-points and end-products and thus 

 introduce a new factor. The constant up-and-down movement 

 of the soluble salts in the soil, the alternate drying and wetting 

 of the soil, and the effects of thermal changes on the soil, may 

 partially obliterate the true effects of washing certain salts from 

 soils. In addition, the relation of calcium, magnesium and other 

 bases to the sodium may be modified by the conditions just men- 

 tioned, so that different equilibria are established. Furthermore, 

 the nature of the soil, especially with respect to the original con- 

 tent of colloidal substances and hydrated silicate complexes, must 

 be taken into account. Thus the effect of draining salts from 

 sandy soils free of colloids may be so small as to pass unrecog- 

 nized, while similar drainage from heavier types of soils would 

 produce marked effects. The colloidal content, too, and the state 

 of diffusion thereof, in our drained alkali lands, may be a direct 

 result of the first natural introduction of the salts into and their 

 subsequent removal from the original soil, the exact physical 

 condition of which may be only surmised. Hence we have no 

 means for securing evidence as to the exact salt effects under 

 natural conditions. 



As suggested by Mayer,*"'' the physical effects resulting from 

 washing sea salts from the soil may be as injurious to the growth 

 of plants as the direct toxicity of the salt itself. Our experience 

 with the cylinders serves to confirm this idea, for despite the 

 fact that the top foot of soil is almost free from salts, it seems 

 impossible to secure a satisfactory growth of plants. A pot 

 experiment, to be reported upon later, also gives substantial 

 proof that the deflocculated soil, comparatively free from salt, 

 offers a far less congenial home for barley plants, at least during 

 the early stages of growth, than the same soil containing as high 

 as 0.3 per cent of NaCl. 



The inability' of the plants to make a satisfactory growth in 

 the highly deflocculated soils appears, from a cursory considera- 

 tion of the conditions, to be due to the lack of available moisture. 

 Although the deflocculated soils may seem to be moist, yet the 

 quantity of water which the plants have at their disposal is 



66 Loc. cit. 



