EXPERIMENT STATION BULLETINS. 613 



CaSO^, CaClj, etc. Stevenson and Brown, (12), have found that there 

 are alkali spots in certain areas in Iowa which are composed mainly 

 of Ca(HCG3),, MgCHCOa),, Na.SO^, NaNOg, etc. 



In a very extensive investigation King, (13), found that the amount 

 of water-soluble salts in soils was high, and varied with the type of soil, 

 the fertilit}', or manurial treatment it had received, etc. The table 

 below shows a typical example as to the magnitude of the salts recover- 

 ed in the water extracts bv the conventional method. These salts are 

 composed of K, Ca, Mg, N63, HPO„ SO,, HCO., CI, and SO,. 



Table 6. Total Salts Recovered from the Surface Foot of Eight Soil Types, 1903. 



Pounds 



per 



million of 



dry soil. 



Pounds 



per 

 acre of 

 dry soil. 



Norfolk Sandy Soil 182.02 



Selma Silt Loam 226.94 



Norfolk Sand 167.22 



Sassafras Sandy Loam 199 . 70 



Hagerstown Clay Loam 590 . 3 



Hagerstown Loam 532 . 15 



Janesville Loam 468 . 19 



Miami Loam 419.23 



654.4 



788.6 



599.7 



682.3 



1,670.0 



1,532.0 



1,330.00 



1.301.00 



It will be readily seen that the quantity of soluble salts dissolved into 

 the water extract is really high. Of course the investigation does not 

 show in what form these compounds exist in the soil, whether in solu- 

 tion or in solid form, but readilv soluble. If these acids and bases, 

 however, unite to form salts which have a high solubility, there is no 

 reason to doubt why the}- should not be in solution. 



In performing leaching experiments various investigators have found 

 that the first portion of the water passing through the dry soil always 

 contains a far greater concentration than the subsequent leachings. 

 The subsequent leachings finally reach a low degree of concentration 

 which tends to remain constant. The higher concentration of salts in 

 the first washings is attributed by some investigators to the decrease in 

 absorbtive power of the soil for the salts, due to the process of drying. 

 It could be equally attributed to the presence of readily soluble salts. 



Furthermore, that salts of high solubility may exist in the soil solu- 

 tion is further confirmed by the reaction that is conceived to take place 

 between the soil and a soluble salt added. Thus, Alx Fex Mgx Nax 

 Ca(Si03)x (H,0)x + 2KC1 = Alx Fex Mgx Nax K,(SiO,)x (H,0) 

 + CaClo. The CaClo is assumed to be in solution. 



The evidences, therefore, of the existence of salts of high solubility 

 in the soil solution are very strong. The solubilities of some of the 

 salts that are likelv to occur in the soil solution are shown in 

 Table 6. 



('2) Bul. 1,57, Ta. Agr. E.xpt. Sta.. 1915. 



(") Bul. 26, Bureau of Soils, U. S. Dept. of Agr., p. 67, 1905. 



