Land Plaster for Black Alkali 285 



troubled with black alkali in not too large quantities, 

 land plaster could be used as a fertilizer, which would 

 have the effect of changing the sodium carbonate into 

 the less harmful sodium sulphate, and in this way 

 transform sterile lands into those which are capable 

 of being worked at a profit. He clearly saw, however, 

 that such a remedy was not an absolute corrective, 

 but rather of the nature of a substitution of a lesser 

 for a greater evil, as, sooner or later, the sodium sul- 

 phate comes to be too strong to be endured. 



Hilgard has further pointed out that the application 

 of land plaster to a soil rich in sodium carbonate very 

 greatly improves the texture or mechanical condition 

 of such a soil, because black alkali tends to break 

 down the granular structure of clay soils, and thus 

 puddles them and renders them nearly uninhabitable 

 by most plants, largely on account of their bad 

 mechanical condition. 



Still further has Hilgard pointed out that the pres- 

 ence of black alkali in a soil -water tends to dissolve 

 the humic nitrogen and the comparatively ^insoluble 

 phosphates of the soil, so that if leaching is taking 

 place under the influence of a water containing much 

 sodium carbonate, great harm is being done by depriv- 

 ing the soil of two of its most important ingredients 

 of plant -food. Hence if alkali lands are to be im- 

 proved by drainage, this should not be done until 

 steps have been taken to first transform the sodium 

 carbonate to the sulphate, and thus precipitate the 

 humic nitrogen and the phosphate so that these may 

 be retained. 



