152 HORTICULTURE FOR SCHOOLS 



for the water increases, its value grows in proportion, and 

 adjustments that are fair to all become more and more 

 difficult. The problem applies not only to water diverted 

 from streams or stored in reservoirs, but to the underground 

 water as well. 



248. Moderation in irrigation. Too much water may 

 be as disastrous in irrigation practice as too little. "The 

 best way to irrigate," says one writer, "is with a rake," 

 meaning that the best method to conserve moisture is by 

 frequent and thorough cultivation. But where irrigation 

 water is abundant and cheap, the temptation is always 

 present to use the water rather than the cultivator. This 

 causes poor soil conditions, a rising water-table or the wast- 

 ing of plant-food through leaching. These serious conse- 

 quences are in many cases preventable, and serve as stern 

 reminders of the necessity of intelligence in the use of irriga- 

 tion water. 



249. Alkali. All water that has flowed over or through 

 the ground carries a greater or less .quantity of mineral 

 salts in solution. When the water is evaporated by the sun, 

 the mineral salts are left behind, and these give rise to the 

 so-called alkali soils. There is especial danger from this 

 source in irrigated regions, for such localities are receiving 

 fresh supplies of mineral salts with each irrigation. In regions 

 of abundant rainfall, the excess water would wash the ground 

 free from these salts; but in arid or semi-arid climates the 

 matter accumulates year after year and decade after decade, 

 becoming always more concentrated. 



There is only one practical way to remove alkali and that is 

 by drainage. Tiles are employed for the purpose in the same 

 way that they are used in other regions for carrying off surplus 

 water; and already the matter of tile drainage is coming up 

 for serious consideration in many of the irrigated parts of 

 the United States. 



250. Drainage has for a long time been recognized as of 



