TREATMENT OF ALKALI LAND 223 



acquainted with the position and movements of the injurious 

 salts within the soil ; in this study of the subject, the facts 

 already laid down in the earlier part of the present chapter 

 will find fresh illustration. 



The first point we have to bear in mind is that the injurious 

 salts are generally confined to a few feet of the soil. This fact 

 appears in the numerous examinations of alkali land to the 

 depth of 4 ft. made in California, and further evidence on 

 the subject is supplied by the purity of the water in the 

 deeper wells sunk in the same district 1 . We have thus to 

 deal with a limited quantity of alkali salts ; and the first 

 and great lesson we have to learn, is that the injurious 

 effect of these salts depends entirely on their position in the 

 soil. 



In 1895 determinations of the quantity of alkali salts in 

 each successive three inches of soil were made in the case of 

 certain typical lands forming part of the Experiment Station 

 at Tulare, California; some of these determinations will be 

 found in Table XXXVIII. 



The unirrigated natural soil mentioned in this table was 

 one not under cultivation ; it was covered in the spring with 

 a luxuriant natural growth of flowers, chiefly annuals, which 

 died down in summer time during the heat and drought usual 

 in that climate. The results of the examination of this soil 

 show that in May the soluble salts formed a well-marked 

 band, the greatest concentration of the salts occurring between 

 30 and 33 inches below the surface ; above and below this 

 point the quantity of salts rapidly diminished. The dis- 

 tribution of the salt in this soil at once reminds us of the 



1 In recent investigations in the Yellowstone Valley the subsoil was found 

 impregnated with salts to a much greater depth than in California. 



