OTHER CHEMICAL TREATMENTS 161 



years following 1897 a six-acre vineyard received 34,000 

 pounds of gypsum or about 4^ tons a year. This was 

 applied at a cost of less than four dollars an acre each 

 year which was a small cost in proportion to the returns. 



As a result of experiments in the San Luis Valley, Colo- 

 rado, Headden (7) suggests the use of nine pounds of 

 gypsum for each pound of black alkali in the soil and the 

 removal of the alkali by surface irrigation. 



Extensive experiments by Breazeale (1) are reported as 

 showing that the field application of gypsum probably 

 has no effect in overcoming black alkali if the soil already 

 contains soluble sulphates in appreciable quantities or if 

 the irrigation water contains these salts. It seems, there- 

 fore that while gypsum is useful under some conditions, 

 it is not by any means a universal panacea for all black- 

 alkali troubles. 



Other Chemical Treatments. The use of chemical 

 substances other than gypsum has frequently been tried 

 in overcoming alkali. Symmonds (17) found in pot ex- 

 periments that alkali soil that was treated with 0.2, 0.5, 

 and 1 per cent of nitric acid produced more than 5 

 times the yield of wheat that was produced by the un- 

 treated soil. He (16) later carried on a similar experiment 

 in the field where 600 pounds of nitric acid to the acre of 

 land were mixed with artesian well water and sprinkled 

 on the soil. The results showed a great increase in yield 

 due to the treatment. 



Lipman (10) has obtained excellent results in treating 

 alkali soil with small quantities of sulphuric acid. 



The use of stable manure on alkali land has long been 

 known to improve it for crop production. It has indirect 

 value in reducing evaporation as well as the more direct 

 action on the soil and plants. 



