1028 EXPERIMENT STATION RECORD. 



"The first sample is a very pure type of sandstone soil taken from the top of the 

 blnff about 2£ miles north, of Billings and was derived from the decomposition of 



the soft layers of line sandstone which cap the blurt's. These soils are very light 

 and loose and have very free underdrainage. As a matter of fact, they leach readily, 

 and, although they afford the best possible conditions for irrigation in that seepage 

 waters are not likely to accumulate in them, it is probable that they would not last 

 very long, as the soluble salts would easily and quickly be removed from them. 

 Soils of this type are found in many parts of the valley, and there is little or no 

 danger from seepage waters or from an accumulation of soluble salts at the sm lace, 

 although they contain considerable quantities of such salts at depths below the 

 surface. 



"The other samples in the table are seen to grade up through the mixed sandy 

 gumbo to the pure form of gumbo with from 27 to 35 per cent of clay. The mixed 

 soiJs are the most abundant in the valley." 



When this valley was first settled, there were no signs of alkali on 

 the surface of the soil, hut now, after 12 to 15 years of irrigation 

 (usually excessive) many once fertile tracts on the lower levels have 

 become flooded, " and alkali has accumulated on them to such an 

 extent that they are mere bogs and swamps and alkali flats.'" 



The alkali in this locality, as indicated above, consists mainly of 

 magnesium and sodium sulphates, with no sodium carbonate and but a 

 trace of sodium chlorid. Its composition, which is very constant 

 throughout the region, is shown by the following average of 5 analyses 

 by F. W. Traphagen: 



Composition of the soluble salts at Billings, Montana. 



Per cent. 



Sodium sulphate 57. 44 



Magnesium sulphate 27. 59 



Calcium sulphate 13. 05 



Potash sulphate 1. 55 



Silica ">3 



99. 99 



In order to determine the amount and distribution of the soluble 

 salts in the different soils, both with and without irrigation — 



"Three lines of borings were run — one of 5 miles in length and the others, for more 

 detailed study, of about 1J miles and one-fourth of a mile, respectively, in length. 

 The longer section began above the ditch and went down toward the river; the others 

 extended from an alkali flat and from a drainage ditch back into the higher levels. 

 In each of these sections a number of borings were made and the salt content deter- 

 mined at every foot in depth down to 10 or, frequently, 15 ft. In addition to this, a 

 section or square mile of land was studied in great detail and borings were made 

 at frequent intervals to a depth of 10 or 15 ft. A number of special borings were 

 also made to study the relation of the different types of soil to the amount and 

 distribution of the salts.'' 



The amount of soluble salts present was determined by means of the 

 electrical apparatus devised by the Division of Soils (E. S. R., 9, p. 535; 

 10, p. 30). The results are given in tables and in a series of charts and 

 maps. The latter show graphically the depth to standing water and the 

 amount and distribution of soluble salts at different depths in the soil 

 of the area examined. "As a result of the investigations at Billings it 



