84 ARID AGRICULTURE. 



accumulation is the result of bad management, 

 generally of over-irrigation or of continuously 

 leaving the water running on the soil. In many 

 parts of the West where the native sod is irri- 

 gated for the production of hay, the water is al- 

 lowed to run for weeks or months over the same 

 land, and such irrigation is apt to produce bad 

 results. Some irrigation waters contain large 

 amounts of alkali salts which are deposited with 

 the water applied. 



EPPECTS OP There are two kinds of alkali which are 



found in different sections of the arid region. In 

 the mountain states where the climate is cool, the 

 white alkali predominates. White alkali is a 

 mixture of the sulphates and chlorides of soda 

 and magnesia. In the warmer regions the alkali 

 is composed of carbonate of soda and is called 

 black alkali. One-tenth of one per cent, of black 

 alkali will prevent the growth of useful plants 

 on the soil, while some crops will stand as much 

 as one per cent, of white alkali salts in the sur- 

 face soil. These alkali salts in small amount 

 are important aids in the fertility of the land. 

 They make plants grow faster and better than 

 where they are not present. The black alkali 

 destroys the soil tilth, puddling it and making- 

 it dark in color. The principal detrimental 

 effect of white alkali seems to be that it retards 

 or prevents the germination of seed. If the salts 

 can be diluted or washed out before planting and 



