^ 



FORMATION OF SODIUM CARBONATE, OR BLACK ALKALI, BY 



PLANTS. ^ 



By Frank K. Cameron. 



INTRODUCTION. 



Considerable attention has been paid within the i)ast few years to 

 the possibility^ of growing- valuable forage crops on some of the alkali 

 soils of the arid West. This subject was first taken up in California.^ 

 The great value of saltbushes for certain soil conditions and for cer- 

 tain kinds of cattle feeding seems to be well established, but as both 

 Hilgard and Goss~ have pointed out there is an element of danger, 

 expressed in the prevalent belief that most of these plants, including 

 the greasewood, chico, and other indigenous plants, convert the less 

 harmful neutral salts, such as sodium chloride and sodium sulphate, 

 into alkali carbonates — that is to say, the less harmful "white alkali" 

 is converted into the more noxious "black alkali," as has been 

 show^n by the presence of sodium carbonate immediately under such 

 plants, whereas no trace of it exists some distance away. It may be 

 possible that the i)lants with their enormous root sj^stems actually 

 gather up minute traces of sodium carbonate, which ma}^ be present 

 in lower depths of soil, gradually causing an accumulation at the 

 surface on the decay of their roots and branches. But the generally 

 accepted hypothesis of the conversion of the neutral salts appears 

 more probable, as will be seen in the course of this paper. It would 

 seem probable that plants growing in launches or mats would be more 

 effective in i^roducing these localized black-alkali spots, but some of 

 the most striking illustrations of this phenomenon have been observed 

 in connection with more upright species, such as SarcohaUiH rermi- 

 culatus, the common "greasewood" of the West. 



In the study of the alkali soils of the arid regions tlie field parties 

 of the Division of Soils have found the local flora of great value in 

 indicating the character of the particular soils where they are found. 

 This apparent relation between the i)lant and the salts present in the 

 soil became of interest in this connection and was referred to the 



^University of California, Agricultural Experiment Station, Bui. No. 125 (1899). 

 2 New Mexico College of Agriculture and Mechanical Arts, Agricultural Experi- 

 ment Station, Bui. No. 23, p. 41 (1897). 



Gl 



