282 



Bulletin 38. 



ply containing 100 parts by weight of soluble salts per 100,000 

 parts of water, would carry on to the land 8167 pounds of salts 

 per acre in one year. 



Comparing this amount with the injurious quantities men- 

 tioned above, it is evident that in a very few years such a water 

 would bring harmful amounts of alkali upon the soil, provided 



Fig. 6. Typical artesian well 6 miles southwest of Pima, Arizona. 



that they all remained. This depends largely on the character 

 of the soil. A light, sandy soil, well drained, will retain but a 

 portion of the alkali from the irrigating water ; but a dense adobe, 

 holding a large amount of water, bringing water by capillary ac- 

 tion from greater depths to the surface where it is evaporated, 

 and draining with difficulty, accumulates much larger quantities 

 of salts. With waters of stated composition, and soils of a cer- 



