B. P. I.— 307. 



THE COMPARATIVE TOLERANCE OF VARIOUS 

 PLANTS FOR THE SALTS COMMON IN ALKALI 

 SOILS. 



INTRODUCTION. 



In Report No. 71 of the Department of Agriculture a an account 

 was given of the results of experiments upon the toxicity of certain 

 salts of magnesium and sodium to young seedlings of the white lupine 

 and of alfalfa. It- was shown that these salts differ greatly in their 

 toxicity when allowed to act upon the plants in pure solutions (i. e., 

 of a single *salt), but that the presence of a second salt, notably cal- 

 cium sulphate, not only greatly increases the endurable concentra- 

 tion of the more toxic salt, but tends to equalize the toxicity of the 

 different salts. Experiments, the results of which have not hitherto 

 been published in full, 6 were afterwards made with maize, and it was 

 found that not only were the critical concentrations of the same salts 

 very different from those previously worked out for the white lupine, 

 but the order of toxicit}^ of the various salts also differed widely. The 

 results obtained by Harter c with nine varieties of wheat show that 

 not only are the critical concentrations for this plant different from 

 those previously established for the white lupine and for maize, but 

 that inside the limits of a species there can be much difference between 

 different varieties in their power of resistance to toxic action. 



Since the publication of this last paper similar experiments have 

 been made with four varieties of sorghum (Andropogon sorghum), two 

 varieties of oats (Avena sativa), two species of cotton {Gossypium 

 harbadense and G. hirsittum), and sugar beets (Beta vulgaris). A 

 majority of the more important field crop plants grown in parts of 

 the United States where alkali soils occur are thus represented in the 

 whole series of experiments.^ 



« Some Mutual Relations Between Alkali Soils and Vegetation, 1902. 



& Although referred to in a brief note in Science, n. s., vol. 17, p. 386, 1903. 



o Bui. 79, Bureau of Plant Industry, U. S. Dept. of Agriculture, 1905. 



^The white lupine was selected for the first experiments, not because it is of any 

 importance as a crop plant in this country, but because of the ease with which it is 

 handled in water-culture experiments. 



7 

 6985— Bui. 113—07 2 



