JOimOFAGiaQnTDRALlSEARCH 



Vol. X "Washington, D. C, September io, 191 7 No. 11 



FORMATION OF "BLACK ALKALI" (SODIUM CARBON- 

 ATE) IN CALCAREOUS SOILS 



By J. F. Breazeale, 



Biophysical Investigations, Bureau of Plant Industry, United States 

 Department of Agriculture 



INTRODUCTION 



It is unfortunate that the term "alkali," when used to designate 

 an accumulation of water-soluble salts in the soil, has come into such 

 common use in the United States. In this paper, this term will be 

 adhered to out of deference to common custom. The term will be used 

 to designate sodium chlorid, sodium sulphate, sodium carbonate, or 

 any of the other water-soluble salts of the soil. As is well known, the 

 term "black alkali" originated from the fact that sodium carbonate 

 acts upon the organic matter of the soil and produces a dark-colored 

 solution. 



The writer is aware of the fact that the presence of calcium carbonate 

 is not necessary in all cases to explain the formation of sodium carbonate. 

 In the decomposition of the basalts, alkaline carbonates are likely to be 

 formed. These carbonates may be transported and may reappear in 

 other areas. The alkaline marshes around Klamath, Greg., are exam- 

 ples of this type of alkali that quite likely did not form in that place. 

 It is the purpose of this paper to discuss only one specific phase of alkali 

 formation, and that is that which takes place when sodium salts are 

 present in a calcareous soil. 



With the exception of an adequate water supply, the presence and 

 accumulation of alkali is probably the most important problem that 

 confronts the man engaged in farming under irrigation in the arid and 

 semiarid regions of the West. The successful reclamation of desert 

 lands is by no means an easy matter, and the handling of the soluble 

 salts that have accumulated in the soil during the centuries that it has 

 been lying in this arid condition offers many difficult problems. 



As ordinarily used, the term "alkali" consists chiefly of the salts of 

 sodium, together with in lesser amounts the salts of calcium and mag- 



Joumal of Agricultural Research, Vol. X, No. n 



Washington. D. C. Sept. lo, 1917 



jo Key No. G — 119 



(541) 



