280 Irrigation and Drainage 



It will be seen from these two tables that there 

 may be associated with the undesirable salts quite 

 notable quantities of others which are valuable plant- 

 foods. This is as should be expected, for the more 

 soluble plant -foods, as well as the salts not suitable 

 for plant life, must be moved by the same waters, 

 and tend to collect with them. 



Hilgard points out that where the soluble phos- 

 phates and considerable quantities of humus are asso- 

 ciated with the sodium carbonate or black alkali, it is 

 often desirable to first transform the sodium carbo- 

 nate into sodium sulphate through an application of 

 land plaster. By so doing both the humus and 

 phosphates are rendered insoluble, but not unavaila- 

 ble for plant -food, hence may be retained in the soil 

 for future use after the alkalies, which are harmful, 

 have been washed out or otherwise disposed of. This 

 is an important suggestion to keep in mind. 



THE APPEARANCE OF VEGETATION ON 

 ALKALI LANDS 



When cultivated crops are grown upon alkali lands, 

 characteristic effects are produced which serve to point 

 out the difficulty with the soil and the remedy which 

 should be applied. If the salts in the soil are not too 

 concentrated, the crop may germinate in a perfectly 

 normal manner, but after a time begin to languish in 

 spots, and remain dwarfed in stature or. entirely die 

 out. It is very common to see a field upon which the 

 crops present an extremely uneven stand, some areas 



