REFERENCES 237 



the purity of the juices and the quantity present was re- 

 duced. In these experiments 6.75 and 8.79 acre-feet of 

 water were applied during the season and occasional heavy 

 irrigations were given to keep the salts from accumulating. 

 When the quantity of water used was reduced considerably 

 so that the strength of the soil solution became high such 

 a large quantity of alkali proved fatal (6) (7). 



Using coffee, cocoa, and other plants to determine the 

 concentration of water that may be used with safety (22), 

 it was found that the limits were between 5000 and 15,000 

 parts per million although the result were somewhat 

 complicated by rainfall. 



From a survey of a number of localities along the 

 Potomac River, Scofield (30) assumes that the salt water 

 limit for wild rice is about 1754 parts per million (0.03 

 normal) for sodium chloride. The growth was just about 

 proportionate to the strength of the solution when less 

 than this amount was present. 



Water to be used in irrigating rice should never contain 

 more than 3000 parts per million of salt, according to 

 Fraps (9) of Texas. 



Harris and Butt (14), after a rather extensive study of 

 the use of alkali water for irrigation, concluded that under 

 average conditions more than 500 parts per million of 

 sodium carbonate, 1000 parts per million of sodium chlo- 

 ride, 4000 parts per million of sodium sulphate, and 4000 

 parts per million of the ordinary mixture of salts are 

 dangerous. In case there were no drainage from the land, 

 lower limits than those mentioned would have to be used. 



REFERENCES 



i. ALLEN, R. W. Work of the Umatilla Reclamation Project Experi- 

 ment Farm in 1915 and 1916. U. S. D. A. Bur. PI. Ind., W. I. A. 

 Circ. 17, p. 17. 



