Soils 67 
Any soluble salt present in sufficient quantities may be 
considered an alkali. The salts most commonly causing 
injury are sodium chloride, or common salt; sodium sul- 
fate, or Glauber’s salt; sodium carbonate, or salsoda; 
and magnesium sulfate, or epsom salt. In addition 
to these, sodium nitrate and a number of other salts 
cause injury in some districts. Sodium chloride is 
injurious to beets when present in lower concentra- 
tions than any of the other salts mentioned; sodium 
carbonate, or black alkali, injures the soil when present 
in low concentrations by dissolving the organic matter and 
causing a hard crust to form. Beets will grow in rela- 
tively large quantities of the sulfates. 
The injury done to crops by alkali salts results largely 
from the shutting off of water from the plant on account 
of the soil solution’s having a greater concentration than 
the plant-cells. By the law of osmosis, water passes 
from the dilute to the more concentrated solution. In a 
normal soil the root has a cell-sap with a higher concen- 
tration than the soil solution; hence water passes from the 
soil into the plant. When the soil solution is made too 
concentrated, water passes out of the roots into the soil 
and the plant dies. 
The permanent reclamation of alkali lands rests on the 
removal of the excessive salts by drainage. The methods 
of accomplishing this are discussed in Chapter X. Where 
the accumulation of alkali results from the over-irriga- 
tion of higher lands, the remedy is obviously the preven- 
tion of percolating water, which carries soluble salts from 
the higher and concentrates them in lower lands. Any 
practice that reduces evaporation, such as cultivation, 
