402 IRRIGATION PRACTICE 



than 10 feet in depth over the whole area. This quantity 

 of water carried off 5,317 tons of salt, and reduced the 

 alkali content to 13 per cent of what it was at the beginning 

 of the experiment. Not only was this tract of 40 acres 

 reclaimed by this treatment, but the beneficial effects of 

 the drainage were felt in the adjoining fields. 



At Fresno, California, where the predominating type 

 of alkali was a mixture of the chloride and the carbonate 

 of sodium, a hopelessly alkaline tract was restored by tile 

 drainage in less than one year to permanent fertility. At 

 Billings, Montana, where the prevailing type of alkali 

 was sodium sulphate, similar reclamation work was 

 accomplished in two years. These three experiments, 

 at Salt Lake City, Fresno, and Billings, representing the 

 three chief types of alkali, demonstrate the feasibility of 

 reclaiming alkali lands by underdrainage, provided there 

 is a sufficient fall of the land and a suitable outlet. 



Alkali may attack and injure the materials of which 

 the drains are made. When glazed pipe is used, the danger 

 is small; but if concrete or cement pipe is laid, the danger 

 is large, for alkali uniting with the calcium hydroxide 

 of the cement tends to disintegrate concrete. In the de- 

 structive action on concrete, sodium sulfate stands first, 

 followed by magnesium sulfate and then by sodium 

 carbonate. Sodium chloride has a small but definitely 

 injurious effect. 



Alkali lands represent only a small proportion of the 

 total irrigated area. Cautious irrigation of the higher- 

 lying lands will prevent the increase of this area, and 

 underdrainage will reduce it considerably. With our pres- 

 ent knowledge, there is no reason why the "alkali plague" 

 should be feared. Vigorous measures should be taken, 

 however ; if the alkali trouble is approaching. 



