TOXIC LIMITS OF SALTS 235 



saline water has been found better than by the furrow 

 method. This is especially the case where such good 

 drainage prevails that large quantities of water may be 

 applied to leach out any accumulation of salts. Experi- 

 ments have shown that land flooded every 8 days with 

 alkali water contained less than one-third the quantity 

 of alkali found in the temporary ridges under furrow ir- 

 rigation and about 27 per cent of that found in unculti- 

 vated tree rows. 



Hawaiian experiments (7) show that with large applica- 

 tions of water containing about 3430 parts per million 

 (200 grains per gallon) of common salt, large quantities 

 of lime, magnesia, and potash are rendered available. 

 Excessive irrigations to prevent the alkali from accumulat- 

 ing at the surface washed out large quantities of lime and 

 magnesia. Soils not well supplied with lime are injured 

 much more by alkali than those well supplied. It was 

 found in Wyoming (31) that alkali irrigation water caused 

 a considerable loss of calcium sulphate and calcium car- 

 bonate from the soil. Experiments in Oregon (i) show 

 that calcium carbonates and nitrates wash out of the soil 

 faster than supplied in the irrigation water. 



It has been found in some regions that the dissolving 

 action of alkali the chloride and sulphate salts on 

 lime destroys the impervious hardpan layer often found 

 a foot or two beneath the surface, thus allowing drainage 

 to go on more freely. 



In the Southwest, especially in New Mexico, certain of 

 the streams carry calcium sulphate in solution some of 

 the time. The salt neutralizes and makes less toxic the 

 sodium carbonate found at times in the soils of the district. 

 If but little or no black alkali is present, as is the case in 

 that of the Pecos River irrigation water may contain 



