4 BULLETIN 135, U. S. DEPARTMENT OF AGRICULTURE. 



work and of the results so far accomplished. A detailed account of 

 the observations made, the experiments conducted, and the results 

 secured is given in the following pages. 



QUANTITY AND CHARACTER OF THE SALT. 



Determinations of the quantities of salts hi this soil have been 

 made with the electrolytic bridge at intervals since this work was 

 started. The samples on which these determinations were made 

 were taken from six different strata, -as follows: The first 3 inches, 

 3 to 6 inches, 6 to 12 inches, 12 to 24 inches, 24 to 36 inches, and 

 36 to 48 inches. A general idea of the total salt content of the virgin 

 soil can be obtained from the average of 50 samples from each depth 

 taken on five different dates — May 2, June 5, July 16, September 3, 

 and October 23, 1913 — from 10 different places on the tract. The 

 total salt content of the soil of each layer (expressed as a percentage 

 of the air-dry soil) was found to be as follows: Top 3 inches, 0.65; 

 3 to 6 inches, 0.92; 6 to 12 inches, 1.54; average of first foot, 1.16; 

 12 to 24 inches, 1.83; average of top 2 feet, 1.49; 24 to 36 inches, 

 2.08; 36 to 48 inches, 1.79; average of top 4 feet, 1.71. 



It is seen that the salt content of the virgin soil increases rapidly 

 with the depth. The average of 1.71 per cent for the whole 4-foot 

 layer is equal to 111.73 tons of salts per acre. This percentage is 

 too high to permit normal growth of most field crops. Analyses 

 have been made of the salt in the soil samples taken on May 2 1 from 

 10 borings. The results of the analyses (expressed as percentages 

 of air-dry soil) of the 10 composite samples are as follows: Total 

 salts, 1.774; CaO, 0.2374; MgO, 0.0698; N0 3 , trace; Na 2 0, 0.4410; 

 HC0 3 , 0.0360; S0 4 , 1.2386. 



This analysis indicates that the salts are chiefly a mixture of the 

 sulphates of sodium, calcium, and magnesium, and if the results are 

 calculated in terms of these salts they show percentages of salts in 

 the dry soil as follows: Total solids, 1.774; Na 2 S0 4 , 1.0106; CaS0 4 , 

 0.5758; MgS0 4 , 0.2078. 



An analysis of 16 samples of this soil made by Prof. Edmund 

 Burke, of the Montana Agricultural Experiment Station, in 1912, 

 gave the following percentages: Na 2 S0 4 , 1.1284; Na 2 C0 3 , 0.02848; 

 NaCl, 0.01956. These analyses show small amounts of sodium car- 

 bonate and sodium chlorid, neither of which was found in the samples 

 analyzed in 1913. The samples from which the analyses were made 

 in 1912 were taken from a different part of the field and were from 

 specially selected "bad spots." This might account for the differ- 

 ences found. 



1 These analyses and the analyses of ground water shown in Table I were made by Mr. J. F. Breazeale, 

 of the Bureau of Chemistry, United States Department of Agriculture. 



