56 



TOXIC LIMITS OF ALKALI 



resistance during later growth, and the relation between 

 germination and subsequent growth differs for these two 

 salts. 



With the following quantities of alkali added to loam 

 soil the author (10) found the plants indicated in the table 

 to produce about half-normal crops of dry matter. 



TABLE X. QUANTITIES OF VARIOUS SALTS ADDED TO THE SOIL 

 WHICH REDUCED THE YIELD OF CROPS TO ABOUT HALF NORMAL 



It will be noted that the figures by the author are con- 

 siderably above those of Guthrie and Helms, but that the 

 carbonates when added to the soil in each case were less 

 harmful than the sodium chloride. In the sand soil the 

 sodium chloride and sodium carbonate were noted to be 

 nearly equally toxic and for the field results presented in 

 Chapter XIV the sodium carbonate shows nearly the 

 reverse relationship to this. The low toxicity of the 

 salts as compared with those for field determinations are 

 probably due partly to absorption of some of the salts 

 and to the even distribution and favorable moisture content 

 possible in controlled experiments compared with field 

 conditions. Of the salts used in the experiments of the 

 author with wheat seedlings, the order of toxicity for salts 

 added from highest to lowest was as follows: sodium 

 chloride, calcium chloride, potassium chloride, sodium ni- 

 trate, magnesium chloride, potassium nitrate, magnesium 



