222 MOVEMENTS OF SALTS IN THE SOIL 



forms of alkali land (California Station Report, 1894-5, 319). 

 An analysis made by Jaffa (ibid. 165) showed the dry matter 

 of the plant to contain 20-84 per cent, of ash, about 40 per 

 cent, of which was sodium chloride. A crop of 5 tons of dry 

 saltbush fodder would remove 1,360 Ib. of alkali salts from 

 the soil. One mode of ameliorating alkali land is clearly to 

 grow crops of this description, to be afterwards consumed off 

 the soil. 



Treatment of Alkali Land. The successful treatment of 

 alkali land is a problem of great importance owing to the 

 wide areas over which such lands occur. As they are found 

 always in districts having an insufficient rainfall they have 

 been largely treated by irrigation. Instead however of the 

 salts being removed from the land by this treatment, it has 

 often happened, both in India and California, that the system- 

 atic irrigation of a district has largely increased the extent 

 of infertile land. Land not previously known to contain 

 alkali has often a few years after the introduction of irrigation 

 been found covered with patches of alkali, which have gradu- 

 ally extended till the whole area has become sterile. It was 

 at first supposed that the injury thus produced was due to 

 the presence of alkali salts in the water applied to the land ; 

 but although the composition of the water must clearly have 

 an influence on the result, the existence of alkali salts in the 

 water used for irrigation is no sufficient explanation of the 

 injurious results which follow this treatment, for a similar 

 injury is also observed where a perfectly pure water has 

 been employed. The injury thus produced by irrigation is com- 

 monly, and accurately, described as due to a rise of the alkali.' 



To understand the effect produced by irrigation, or to 

 establish any rational treatment of alkali lands, we must be 



