Apr. 28,1923 
Toxicity and Antagonism of Alkali Salts in Soil 
323 
by sodium carbonate alone at 7,500 parts per million, by sodium sulphate 
at 9,500 parts per million, and by a mixture of the two containing 5,000 
parts per million each (fig. 3, C). Considering the fact that there is 
some chemical removal of these salts from the soil solution by the soil 
material (jj, p, 431) so that their concentration is really lower than the 
amount added indicates, these toxicity relations appear to be very nearly 
additive. 
IMI the other mixtures follow the untreated sodium carbonate curve 
much more closely, indicating that they have very little, if any, influence 
on the toxicity of this salt, though the presence of sodium sulphate in 
Fig. 3.—Diagram showing the effect on the growth of wheat plants of adding sulphates to Greenville 
loam already impregnated with an equal total quantity of sodium carbonate. 
them is nearly always made manifest by the somewhat lower position 
of the curve. It is interesting to note that the calcium sulphate when 
mixed with sodium carbonate does not react in the same way in both 
soils. In the Greenville soil it shows no harmful effects at all in con¬ 
junction with the carbonate, whereas in the West Logan soil it seems 
to lower the yield slightly. There is certainly no striking evidence of 
antagonism between any of these substances in either of the two heavier 
soils. 
Figure 5 represents the data for the dry weight per plant obtained by 
treating the Greenville soil, already impregnated with sodium chlorid, 
with sulphuric acid, calcium sulphate, and sodium sulphate. The con- 
