13 



frequently appears on the surface of the soil in the form of a white 

 crust. 



In most irrigated districts water is used in excessive amounts. 

 Usually the farmer, seeing the benefits derived from irrigation, over- 

 irrigates his land, and as a consequence damage arises from the accu- 

 mulation of alkali salts and seepage waters. Few irrigated districts 

 arc entirely free from alkali after irrigation has been practiced for a 

 few years. Little provision is made for the drainage of lands when 

 irrigation canals are built, the only thought then being to supply the 

 lack of water. Usually the amount of strongly impregnated alkali 

 land is so small that little attention is paid to it, and as the ground 

 water is many feet deep the need of drainage channels is not apparent. 

 After a few years of irrigation with excessive amounts of water the 

 water-table rises, in some cases to within 2 feet or less of the surface. 



Then capillary action brings the water to the surface, much as oil 

 rises in a wick, where the water is carried off in the air by evapora- 

 tion and the alkali salts are left on the surface. Here the} 7 accumu- 

 late from year to year, until in some instances a crust several inches 

 thick is formed. Soon deep-rooted crops, such as alfalf, begin to 

 suffer from the rise of ground water, until they are completely drowned 

 out, while the areas of heavily incrusted alkali soils grow appreciably 

 each year. Occasional!} 7 a single season suffices to transform a flour- 

 ishing alfalfa Held into a barren alkali flat. This is not the experience 

 of any single irrigated district, but is the common experience of all 

 irrigated countries of little rainfall. 



Thus it is seen that one of the drawbacks to irrigation farming is this 

 liability to damage from the rise of alkali and seepage waters unless 

 reasonable precautions are taken. If provision were made for carry- 

 ing off the surplus water when the supply canals are first built, the 

 trouble from seepage water and alkali would be reduced to a minimum. 

 By using as little water as possible and by frequent shallow cultiva- 

 tion in the case of crops that leave the soil partly exposed, the danger 

 from accumulation of alkali is lessened. Cultivation materially checks 

 surface evaporation, while the restricted use of water reduces the 

 chances of the deep subsoil becoming saturated so soon after irriga- 

 tion is commenced. Unfortunately, however, few such precautions 

 are taken, and the alkali question becomes more serious from year to 

 year. Even in districts suffering most from this trouble little effort 

 is made to check the spread of alkali. Often from lack of knowledge 

 to fight the evil, or from disinclination to combat it, the farmer aban- 

 dons land that might be kept in profitable cultivation. In many dis- 

 tricts what were formerly the choicest tracts of land are now alkali 

 flats or salt grass pastures. Conservative estimates indicate that on the 

 average from 10 to 15 per cent of the area of every irrigated district 



