Treatment of Sick Soils 31 



Two and a half tons of good wood ashes are equiva- 

 lent to one ton of burned lime for overcoming soil 

 acidity. Leached ashes have lost their potash and 

 its lime is in the form of a hydrate or carbonate. 

 Magnesium lime, which contains a high percent- 

 age of magnesia, is not objectionable for use. In 

 fact, a ton of limestone, which contains magnesium 

 carbonate is more effective on acid soil than a ton 

 of limestone without magnesium carbonate. Lime 

 should be applied only when the acidity of the soil 

 requires it. 



Alkali Soils 



Alkali soils are termed sick, since plants thrive 

 there poorly or not at all. The alkali problem gen- 

 erally concerns only those greenhouse men located 

 in the irrigated districts of the arid or semi-arid 

 regions of the United States. 



For convenience, alkali soils are here divided into 

 black and white. The black alkali lands are known 

 to contain sodium carbonate or washing soda as the 

 essential salt. The latter does not act so much on 

 the soil as on the organic matter, turning it black. 

 This dark material is always found on the surface 

 with the salts. The blackening of the soil, however, 

 is not always an indication of black alkali. Many 

 dark spots are found to contain the white alkali. 

 Moreover, soils which contain little or no organic 

 matter may contain large quantities of sodium car- 

 bonate and never turn black. The white alkali in 

 reality is not a true alkali. The salts found in it 



