Sept. 10, 1917 Formation of "Black Alkali'' 581 



In a recent bulletin of the Utah Experiment Station (4) an attempt 

 was made to determine the amount of alkali necessary to prohibit the 

 growth of certain field crops. Some barren spots, like those described 

 at North Platte, were selected and comparisons made between these 

 spots and good places in the same or adjoining fields, and the assumption 

 was made that the barrenness of the poor spots was due to the common 

 "alkali" salts. In the light of the results here presented, the present 

 writer seems justified in suggesting the possibility that conditions other 

 than alkali might enter into the barrenness of these spots. 



The difference in the solubility of the salts formed in the reactions 

 between the sodium salts and calcium carbonate, and the difference in their 

 rate of movement through the soil is responsible in a large measure for 

 the accumulation of the different salts on the surface in different places. 

 We may have "black alkali" spots, in which sodium carbonate pre- 

 dominates, or the so-called "slick spots," in which calcium carbonate 

 predominates, or the so-called "niter spots," in which calcium nitrate 

 predominates. 



The presence of black alkali, or sodium carbonate, in such small amounts 

 as 0.1 to 0.05 per cent renders some soils unfit for cultivation. The inju- 

 rious effects on field crops, generally attributed to sodium carbonate, is, 

 as has been shown, often out of proportion to what might be expected 

 from results obtained from studies in pure solutions. In the presence of 

 the organic matter and silica of the soil the sodium carbonate is likely 

 to enter into combination not only with the organic matter but with the 

 silica of the soil, as fast as it is formed. In such cases its very presence 

 is often overlooked, existing, as it does, in such small amounts. Enough 

 carbon dioxid is usually added with the distilled water used in making 

 the soil extract for analysis to convert the sodium carbonate to bicar- 

 bonate. It thus fails to show color with phenolphthalein, and the soil 

 is said to contain no sodium carbonate. It does exist, however, in what 

 might be termed a transition state between its formation and its combi- 

 nation with the silica or organic matter. 



In its action upon the finely divided material of the soil the character- 

 istic puddling or cementing is likely to take place. This action usually 

 occurs in spots and is not often extended over wide continuous areas. 

 Many of the barren spots in the semiarid areas are probably due not to 

 the accumulation of alkali, but to the cementing action of sodium car- 

 bonate. The soil puddles, will not take water, and thereby soon becomes 

 barren, the barrenness being due primarily to lack of water. Some excel- 

 lent work has been done by Headley, Curtis, and Scofield (5) at Fallon, 

 Nev., along this line. 



In the humid regions the accumulation of injurious compounds in the 

 soil is not a question of much importance. This is being taken care of 

 by the rains, which make the movement of the soil water downward 

 through the subsoil. The injurious bodies are then leached out. In the 



